(5 *(3^3-8))/6*8(3+4) -21 I am assume is the problem. Several signs are missing but I will do the best I can.

5(27-8)/48(7)-21 = 5(21)/336 - 21 = 105/315 = 1/3 (divide top and bottom by 105). if the signs are all correct. I am assume the blanks in between 6 and 8 and 5 and (3^3) means multiplication and the sign between (3 and 4) means addition. Hope I got all the signs right.