Question 1081555
let's call the trucks a and b (you can call them x and y)
a + b = 28 subtract b from both sides:
a = 28 - b
and
4.5a + 11b = 204 substitute here for a:
4.5(28 - b) + 11b = 204
126 - 4.5b + 11b = 204
6.5b = 78
b = 12
So truck b made 12 trips
Truck a = 28-12 = 16 trips