The ratio of Skid's pennies to Mickey's pennies was 6 to 5. Skid gave half of his pennies to Mickey. He counted his remaining pennies and found that he now had 15 fewer pennies than Mickey. How many pennies did Skid have at first?
Let M be the number of pennies that Mickey has initially
Then (6/5)M = Skid's pennies originally
So
(6/5)M - (1/2)(6/5)M + 15 = M + (1/2)(6/5)M simplify
(6/5)M + 15 = M + (1/2)(6/5)M + (1/2)(6/5)M
(6/5)M + 15 = M + (6/5)M
15 = M = the number that Mickey had originally
(6/5)(15) = 18 = the number that Skid had originally
Proof ....when Skid givess 1/2 of his pennies to Mickey.....Mickey has 15 + 9 = 24 pennies and Skid has 9......so.....Skid has 15 fewer pennies than Mickey