The problem says L - W = 10, (1) (L+2*3)*(W+2*3) - L*W = 402. (2) Simplify (2). It is equivalent to (L+6)*(W+6) - LW = 402, LW + 6L + 6W + 36 - LW = 402, 6L + 6W = 402 - 36 = 366, 6*(L+W) = 366 ====> L + W == 61. So, the problem is equivalent to these two equations L - W = 10, L + W = 61. ------------------Add the equations (both sides). You will get 2L = 10 + 61 = 71 ====> L = = 35.5. Answer. The dimensions of the oil painting are 35.5 inches (length) and 25.5 inches (width).