There should be no problem in finding the value of the unknown variable "b" in the equation given in the question.The equation is solvable for finding the value of "b" because it is the only unknown variable in the single equation that is given in the question.
45 = 3b + 69
Let us reverse both sides of the equation first. then, we get
3b + 69 = 45
3b = 45 - 69
3b = - 24
b = - (24/3)
= - 8
So from the above deduction, we can easily conclude that the value of b in the given equation is -8.