multiple input search from usermeta tables

Is there a way to pass multiple input value to search result page? My code below and I really struggling how to do this. It only work if first name is search however I am having problem if other input fields is added to the search.

My Input search:

first_name
age
section

<form method="get" id="searchform" action="<?php echo home_url( '/' ); ?>">
		    <fieldset id="custom_search">
		    <legend>Custom Search</legend>
		        <label for="s">Search for First Name (required)</label><br/>
		        <input type="text" name="s" id="s" value="search for name.." onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;"/><br/>
		        <input type="image" alt="Search" src="<?php bloginfo( 'template_url' ); ?>/images/search.png" /><br/>

		        <label for="age">Search according to Age (optional)</label><br/>
		        <input type="text" name="age" id="age" value="search for age.." onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" />
		        <input type="image" alt="Search" src="<?php bloginfo( 'template_url' ); ?>/images/search.png" /><br/>

		        <label for="gender">Search according Gender (optional)</label><br/>
				<input type="text" name="gender" id="gender" value="search gender.." onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" />
		        <input type="image" alt="Search" src="<?php bloginfo( 'template_url' ); ?>/images/search.png" /><br/>

		        <label for="section">Search for Section (optional)</label><br/>
				<input type="text" name="section" id="rate" value="section...." onfocus="if(this.value==this.defaultValue)this.value='';" onblur="if(this.value=='')this.value=this.defaultValue;" />
		        <input type="image" alt="Search" src="<?php bloginfo( 'template_url' ); ?>/images/search.png" /><br/>

		    </fieldset>
		</form>

My search.php query code

<?php

	global $wpdb;
	$fname= preg_replace( '/[^0-9]/', '', $_GET['s'] ); //only allow numbers
	$age = preg_replace( '/[^0-9]/', '', $_GET['age'] );
        $section = preg_replace( '/[^0-9]/', '', $_GET['section'] );

	if ($fname!= '')
	{
	//Process Inputs
			$query = "SELECT user_id FROM $wpdb->usermeta
				WHERE ( meta_value LIKE '%%$fname%%' )
				AND ( meta_key = 'first_name' )
				AND user_id IN ( SELECT user_id FROM $wpdb->usermeta WHERE (meta_value= 'student') AND (meta_key = 'entity'))";

			$query_fname = $wpdb->get_results($query);

			//Display Header Title
			echo '<h2>' . 'Students List' . '</h2>';

			foreach ($query_fname as $query_fname1 ) {

			//Query User Information
				$userinfo=get_userdata( $query_fname1->user_id );

			//Display Results
			echo '<li>' . $userinfo->first_name . ' ' . $userinfo->last_name . '</li>';
					}

Currently it display only according to first name search.

What I need to query the results if the user filled up other fields.