Question 401357
We have the system


a + b + c = 251
a + b = c + 45
c = a + 42


Substituting the second equation into the first, we obtain


(c + 45) + c = 251 --> 2c + 45 = 251 --> c = 103. Replacing c into the third equation we get a = 61, and it follows that b = 87.