They both earn the same salary. Call it ' S '.
After Todd spent 716, he had (S - 716) left.
After Zack spent 128, he had (S - 128) left.
The question says that Zack has 4 times as much as Todd has, so
(S - 128) = 4 times (S - 716)
Eliminate parentheses on the right side:
S - 128 = 4S - 2,864
Subtract ' S ' from each side:
-128 = 3S - 2,864
Add 2,864 to each side:
2,736 = 3S
Divide each side by 3 :
912 = S
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Check:
After Todd spends 716, he has (912 - 716) = 196 left.
After Zack spends 128, he has (912 - 128) = 784 left.
784/196 = exactly 4 times.
yay !
