Question

Ethan sold some watches at $14 SGD each and 20 bookmarks at $1.5 SGD each .Roy sold the same amount of watches at $13.50 SGD each and 20 bookmarks at $1.80 SGD each. They collected the same amount of money .How Many watches did he sell?

Answer 1

Suppose the number of watches = x

Then,
Total money earned by Ethan = money earned from watches + ... from      bookmarks
                                               = 14x + 1.5 x 20 ----> 01

Total money earned by Roy = 13.5x + 1.8 x 20 ----> 02

01 = 02
14x + 30 = 13.5x + 36
0.5x = 6
x = 12