Question

A store owner spends 7x + 13 dollars on two orders of boxes of light bulbs, including shipping.

Part A
If she spends 3x + 5 dollars on the first order of light bulbs, which of the following represents how much she spends on the second-order?
10x + 18
4x + 8
21x + 65
10x + 8
Part B
If the store owner spent a total of $90 on both orders, how much does a box of light bulbs cost in dollars? Enter the number in the box.

Answer 1

`B = 4x + 8`

A box = $11

Explanation:

Given

`Total = 7x + 13`

Represent the first order with A and the second with B.

So, we have:

`A = 3x + 5`

Solving (a): Find B.

To find B, we make use of:

`A + B = Total`

Make B the subject

`B = Total - A`

Substitute values for Total and A

`B = 7x + 13 - (3x + 5)`

Open bracket

`B = 7x + 13 - 3x - 5`

Collect Like Terms

`B = 7x - 3x + 13 - 5`

`B = 4x + 8`

Solving (b): Cost of a box of light bulb

This means that:

`Total = 90`

Substitute 7x + 13 for Total

`7x + 13 = 90`

Collect Like Terms

`7x = 90 - 13`

`7x = 77`

Make x the subject

`x = (77)/(7)`

`x = 11`