A local bookstore tracked the type of payments people make at their store. Out of 100 people, 40 paid with cash, 55 paid with a credit card and 5 used a gift card. Based on this information, what is a reasonable prediction of the number of people paying with cash if they had 600 customers?

240

Step-by-step explanation:

Set up a proportion.  Out of 100 people, 40 people paid with cash.  Out of 600 people,  x people paid with cash.

Cross multiply and solve for x.

240 customers paid with cash.

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18