Introduce the variables and set up the system of equations: Rafael and Lucas go to the mall. The two of them buy a total of 15 t-shirts. Rafael gets 3 less than twice as many t-shirts than Lucas. How many t-shirts did each of them get?

lucas = 9

rafael = 6

Step-by-step explanation:

two equations can be derived from the question

r + l = 15 equation 1

r = l - 3  equation 2

r = rafael

l = lucas

substitute for r in equation 1

l - 3 + l = 15

combine similar terms

l + l = 15 + 3

2l = 18

l = 9

substitute for l in equation 1

r + 9 = 15

r = 15 -  9

r = 6