Answer
a whole pepperoni pizza contains 660 calories
a whole ham and pineapple pizza contains 580 calories
Work Step by Step
Let x be the toal calories from a whole a pepperoni pizza
Let y be the total calories from a whole ham and pineapple pizza
Given: $\frac{1}{2}$x+$\frac{3}{4}$y=765
$\frac{1}{4}$x+y=745
Multiply the second equation to 2: 2 ($\frac{1}{4}$x+y=745) =>
$\frac{1}{2}$+2y=1490
Use second question to subtract first equation: ($\frac{1}{2}$x+2y=1490)-($\frac{1}{2}$x+$\frac{3}{4}$y=765) => $\frac{1}{2}$x-$\frac{1}{2}$x+2y-$\frac{3}{4}$y=1490-765 => $\frac{5}{4}$y=725 => y=580
Substitue value of y into first equation to find x: $\frac{1}{2}$x+$\frac{3}{4}$(580)=765 => $\frac{1}{2}$+435=765 =>$\frac{1}{2}$x=330 => x =660
Solution: x=660, y=580
