Find the three numbers in a row where two times the first number increased by six times the third number is the same as three times the second number plus 89

we call : a, b, c - the numbers in a row                      a
                                                                             b = a + 1
                                                                             c = a + 2
2a + 6c = 3b + 89

2a + 6(a+2) = 3(a+1) + 89

2a + 6a+ 12 = 3a + 3 +89

8a + 12 = 3a + 92

8a - 3a = 92 - 12

5a = 80

a = 80 : 5                   b = a+1  ⇒ b = 16 + 1 ⇒ b = 17

a = 16                        c = a+2  ⇒ c = 16 + 2  ⇒ c = 18