Answer: There are 20 veggie burgers.
There are two ways you can solve this:
Let x represent turkey burger and y for veggie burger.
2x + 1.50y = 90
x + y = 50
Work:
-2(x + y = 50)
-2x + -2y = -100
2x + 1.50y = 90 << Add like terms
+ -2x + -2y = -100
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-0.50y = -10 << Solve for y
y = 20
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Let x represent turkey burger and y for veggie burger.
2x + 1.50y = 90
x + y = 50 << Solve for x
x = 50 - y << Plug in y for 2x + 1.50y = 90
2(50 - y) + 1.50y = 90
100 - 2y + 1.50y = 90
-0.50y = -10
y = 20