Let's solve the equation step by step:

13(a-2) + 87(a+1) = 3,495

Expanding both terms:

13a - 26 + 87a + 87 = 3,495

Combining like terms:

100a + 61 = 3,495

Subtracting 61 from both sides:

100a = 3,434

Dividing by 100:

a = 34.34

Therefore, the solution to the equation is a = 34.34.