Answer:
17 adult shirts were sold
Step-by-step explanation:
x = adult shirts and y = children shirts
x + y = 40......adult shirts + child shirts = 40 total shirts
17x + 13y = 588...$ 17 for each adult shirt (x) + $ 13 for each child shirt (y) = $ 588
these are the equations we will be using.
now lets rearrange the first one....x + y = 40......x = 40 - y.....now sub 40 - y in for x back into the second equation
17x + 13y = 588
17(40 - y) + 13y = 588
680 - 17y + 13y = 588
-17y + 13y = 588 - 680
-4y = - 92
y = -92/-4
y = 23 <=== so there were 23 child shirts sold
x + y = 40
x + 23 = 40
x = 40 - 23
x = 17 <===== and 17 adult shirts sold
check...
17x + 13y = 588
17(17) + 13(23) = 588
289 + 299 = 588
588 = 588 (correct)
= 81°