Jackie and Rachel both worked during last summer and made $960 each. Rachel worked 16 hours more than Jackie, but Rachel earned $2 less per hour. How many hours did Jackie work?

The number of hours Jackie worked  = 80hours

Step-by-step explanation:

Last summer:

Jackie made $960

Rachel made $960

let number of hours Jackie worked = x

Rachel worked 16 hours more than Jackie:

Number of hours Rachel worked = x + 16

if Jackie earned $y  per hour

Rachel earned $2 less per hour = y-2

Jackie: 960 = x × y = xy

Rachel: 960 = (x+16)(y-2)

960 = xy -2x +16y -32

recall xy = 960, insert the value for xy

960 = 960 - 2x +16y -32

- 2x +16y -32 = 0

2x -16y = -32

x-8y = -16

x = 8y-16

recall xy = 960, insert the expression for x

(8y-16)y = 960

8y² -16y = 960

y² -2y - 120 = 0

y²+10y-12y -120 = 0

y(y+10) -12(y+10) = 0

(y-12) = 0 or (y+10) = 0

y = 12 or -10

since y can't be negative, y = 12

x = 8y-16

x = 8(12) -16 = 80

The number of hours Jackie worked = x = 80 hours