Let a = 4b + 5(c - b). Find the value of c when a = 8 and b = 7.

a = 4b + 5(c - b) - question8 = (4*7) + 5(c - 7) - insert values given in question8 = 28 + 5c -35 - multiply and expand brackets8 - 28 + 35 = 5c - take away 28 from the left and right-hand side of the equation. Add 35 to the left and right-hand side also15 = 5c - simplify15/5 = c - divide right hand side by constant on left hand side so the variable c is on its own3 = c - answer