You have $60 and your sister has $90. You are planning to save $8 per week and your sister is planning to save $5 per week. How long will it take before you and your sister have the same amount of money?

68 76 84 92 100 108 116 124 132 140

95 100 105 110 115 120 125 130 135 140

each of the groups of numbers represent one week what you do is add eight to 60 and then 5 to 90 and keep on doing that until you get the same number

It will take 10 weeks to have the same amount of money. 60+8*10=140 and 90+5*10=140.