Question

Liam is saving up for a new cell phone. He uses the equation P = I + HB, where P is the cost

of the phone, I is the amount of money he started with, H is the number of hours he babysits,
and B is his hourly rate for babysitting. Which expression is equal to H, the number of hours
Liam will need to babysit to save enough money for a cell phone?

Answer 1

H = (P - I ) / B

Explanation:

Given that : P = I + HB, where P is the cost of the phone, I is the amount of money he started with, H is the number of hours he babysits, and B is his hourly rate for babysitting.

We need to make H the subject of the formula, this is done by rearranging the formula so that H would be the subject. We just have to apply inverse operation to the equation to do this.

P = I + HB

Subtracting I from both sides:

P - I = I + HB - I

P - I = I - I + HB

P - I = HB

Dividing through by B:

(P - I ) / B = HB / B

H = (P - I ) / B