Substitution (One solved for a variable)

Question

Bill and Ted are each saving money for a trip to Europe. Bill started with $75 and saves an additional $15

per week. Ted began with $120 and saves an additional $10 per week. After how many weeks, x, will

they have the same amount of money saved? Explain how you arrived at your answer.

Answer 1

75 + 15x = 120 + 10x, where x is the # of weeks

first, subtracts 10x:

75 + 5x = 120

next subtracts 75:

5x = 45

So then:

x=9

after 9 weeks:

Bill will have 75 + 15*9 =

75 + 135 =

210

Ted will have 120 + 10*9 =

120 + 90

= 210