Apply PEMDAS (order of operations rules). You MUST mult. or div. before you add or subtr.
7/2 - 4.5(3) + 8 becomes
3.5 - 13.5 + 8. Add 3.5 and 8, and then subtr. 13.5 from that sum:
or combine 3.5 and - 13.5, obtaining -10, and then add 8 to the result:
-10 + 8 = -2 (answer)