设兔有x只.
4x + 2(x + 25) = 158
4x + 2x + 50 = 158
6x = 158 - 50
6x = 108
x = 108 ÷ 6
x = 18
鸡：18 + 25 = 43只
答：则鸡有（43）只,兔有（18）只.