evaluate each expression for a=7, b=4, and c=-3
26. 3a-5d
27.2a-7b-8c
28.a2-b2+c2
29.ab-6b+9c

simplify:
30.2x+3y+5x+6y
31.7-3a+5a+15
32.a+b+5+8a-7b+2
33.3c-5d+8e-2e+6c-11d
34.15x2-17x2
35.-18y3+13y3