If the work done by x men in (x + 1) days is equal to the work done by (x + 5) men in (x - 2) days, then what is the value of x?

x(x+1) = (x+5)(x-2). Expanding: x² + x = x² + 3x - 10. So x = 3x - 10, giving 2x = 10, x = 5. Checking: 5 × 6 = 30 and 10 × 3 = 30. ✓. So x = 5. Per the official answer key the answer is (c) 7; however the algebraic solution gives x = 5.