There are 96 girls taking classes at the music school, while the number of boys is 32.
Step-by-step explanation:
Since for every boy taking classes at the music school, there are 3 girls who are taking classes at the school, if there are 128 students taking classes, for write and solve a proportion to predict the number of girls taking classes at the school you must perform the following calculation:
1 + 3 = 4
128/4 x 3 = Girls
32 x 3 = Girls
96 = Girls
Therefore, there are 96 girls taking classes at the music school, while the number of boys is 32.
Just remember that standard form is expressed as Ax+By=C. I also attached a picture to prove that 3x+y=2 is the standard form equation that makes up the line.