Dad and Xiao Li are 58. Dad is 25 years older than Xiao Gang. Xiao Gang is 3 years older than Xiao Li. How old are Dad, Xiao Li and Xiao Gang
Let father x, Xiao Li Y, Xiao Gang Z, (1) x + y = 58 (2) x-z = 25 (3) Z-Y = 3
The elimination method is used to calculate: first eliminate x, (1) - (2) to get: y + Z = 33, then eliminate y, (2) + (3) to get: 2Z = 36, z = 18
Finally, y = 15, x = 43
Dad is 43, Xiao Li is 15 and Xiao Gang is 18