Janet paid $50.40 for two bottles of shampoo and five bottles of body wash. Given that a bottle of body wash is $3.78 cheaper than the bottle of shampoo. How much does a bottle of shampoo cost?

Answer 1

2s +5b = 50.4

b=s-3.78

replace b by s-3.78 in 1st equation to get:

2s + 5(s-3.78) = 50.4

2s+5s = 50.4 +5(3.78)

7s = 50.4 + 18.90

s= 69.30/7= $9.90 for shampoo

b = 9.9-3.78 = $6.12 for body wash

check the answer

2s+5b = 50.4

2(9.9) + 5(6.12)

= 19.8 + 30.6

= 50.4

Answer 2

This is a system of equations. You can assign one variable to be the cost of shampoo (s) and one to be the cost of body wash (b). When you convert the two sentences to two equations you get:

50.40= 2s + 5b

b= s - 3.78

You can plug in the second equation into the first to get:

50.40= 2s + 5(s-3.78)

50.40= 2s + 5s - 18.9

50.40 + 18.9 = 7s

69.3 = 7s

s = 9.90

You can then plug that back into the second equation

b= 9.90-3.78

b=6.12

You can check your work by plugging both values into the first equation

50.4 = 2*9.9 + 5*6.12