Question

A belt and a wallet cost $42, while seven belts and four wallets cost $213.

A) how much do four belts and four wallets cost?
B) how much do three belts cost?

Answer 1

b + w= 42
7b+4w=213

-7b-7w=-294
7b+4w=213

-3w=-81

w=27

b + 27= 42

b= 15

four belts total $60
four wallets total $108

three belts total $45

Answer 2

Let, the cost of a belt = x
cost of a wallet = y

Then, system of equations would be:
x + y = 42
7x + 4y = 213

Multiply 1st equation by 4,
4x + 4y = 168
Substitute it from 2nd equation,
3x = 45
x = 15

Now, substitute it in 1st equation,
15 + y = 42
y = 42 - 15 = 27

In short, Belt costs $15 and wallet costs $27

A)
15x4=60
27x4=108
60+108=
four belts and four wallets cost 168

B) 3x15=
three belts cost 45