Ex.4.
a + b + c = 200
b + 35 = a
b + 45 = c
Inlocuim in prima ecuatie:
b + 35 + b + b + 45 = 200
3 x b + 80 = 200
3b = 200-80
3b = 120
b = 120:3
b = 40
a = 40+35
a= 75
c = 40+45
c = 85
75 + 40 + 85 = 200
Ex.5.
f + b = 29
f = b + 3
b + 3 + b = 29
2b + 3 = 29
2b = 29-3
2b = 26
b = 26:2
b = 13
f = 13+3
f = 16
