Each​ month, a shopkeeper spends 8 x plus 15 dollars on rent and electricity. If she spends 3 x minus 7 dollars on​ rent, how much does she spend on​ electricity? Use pencil and paper. For which​ value(s) of x is the amount the shopkeeper spends on electricity less than​ $100? Explain how you found the​ value(s).

Respuesta :

Answer:

x <  15.6

Step-by-step explanation:

She spends on rent and electricity

P(x) = 8x + 15

She spends on rent

Q(x) = 3x - 7

She spends on electricity

R(x) = P(x) - Q(x) = (8x + 15) - (3x - 7) = 5x + 22

R(x) = 5x + 22

If   R(x) < $ 100  we get

5x + 22 < 100

⇒  5x < 78

⇒  x <  15.6

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