Step-by-step explanation:
[tex]\frac{9}{12} =\frac{15}{x+15}[/tex]
[tex]\frac{3}{4} =\frac{15}{x+15}[/tex]
3(x+15)=60
3x+45=60
3x=15
[tex]\frac{3x}{3} =\frac{15}{3}\\[/tex]
[tex]x = 5\\[/tex]
or..
[tex]\frac{9}{12} =\frac{15}{y}[/tex]
[tex]\frac{3}{4} =\frac{15}{y} \\3y=60\\\frac{3y}{3} =\frac{60}{3} \\y = 20[/tex]
