Question

12-a/12=a/5

Answer 1

12-a/12=a/5（两边同时乘以60）
720-5a=12a
17a=720
a=720÷17
a=720/17

Answer 2

12 - a/12 = a/5
a/12 + a/5 = 12
5a/60 + 12a/60 = 12
17a/60 = 12
17a = 720
a = 720/17