Add 26.40 + 257.60 = 284 , divided by 8 284\8=35.5 , since her total was 284 before she had pay her friend Janet the 26.40 , you divided by the number of months she’s been saving her money which is 8. To check that this is correct simply multiply 35.5 x 8 = 284 subtract that by the money she gives Janet and now she’s at 257.60, so her monthly allowance is 35.5. Easy.