$mRating = total ALL mRating scores here
$mReview = total ALL mReview scores here
$gRating = total ALL gRating scores here

$totalScore = $mRating + $mReview + $gRating;

$mRatingWeighted = ((($mRating * 1.0) / $totalScore) * $mRating);
$mReviewWeighted = ((($mReview * 0.75) / $totalScore) * $mReview);
$gRatingWeighted = ((($gRating * 0.85) / $totalScore) * $gRating);

$totalScoreWeighted = $mRatingWeighted + $mReviewWeighted + $gRatingWeighted;

echo $weightedScore;