a + b + c = 120
a = (b + c) : 2
b - c = 25 = > b = 25 + c
a = (b + c) : 2
a = (25 + c + c) : 2
a =( 25+ 2c) : 2
(25 + 2c) : 2 + 25 + c + c = 120 /x2
25 + 2c + 50 + 2c + 2c = 240
6c = 240 - 75
6c = 165
c = 165 : 6
c = 27,5 cm
a = (25 + 27,5 x 2) : 2= 80 : 2 = 40 cm
b = 25 + 27,5 = 52,5 cm
40 + 52,5 + 27,5 = 120 cm