When having an ordered pair, we say they are in direct variation if the quotient:
[tex]\frac{y}{x}[/tex]is constant. For case 1 we have:
[tex]\frac{80}{32}=\frac{100}{x}[/tex]we can solve for "x" by multiplying by "x" on both sides:
[tex]\frac{x80}{32}=100[/tex]Now we multiply by 32/80 on both sides:
[tex]x=\frac{100\times32}{80}[/tex]Solving the operations we get:
[tex]x=40[/tex]For case 2 we have:
[tex]-\frac{7}{-28}=\frac{y}{20}[/tex]Now we solve for "y" by multiplying by 20 on both sides:
[tex]\frac{-7\times20}{-28}=y[/tex]Solving the operations:
[tex]y=5[/tex]