Please help 7th grade math and an explanation for the answer would be greatly appreciated

x = 20

<f =  80

<g =100

Step-by-step explanation:

<f and <g are supplementary so they add to 180

5x-20 + 3x+40 = 180

Combine like terms

8x+20 = 180

Subtract 20 from each side

8x+20-20 = 180-20

8x = 160

Divide by 8

8x/8 = 160/8

x = 20

<f = 5x-20 = 5*20 -20 = 100-20 = 80

<g = 3x+40 = 3*20 +40 = 60+40 = 100

40 minutes

step-by-step explanation:

add the time and multiply by 2