Answer :
1) If x = 6
Substitute 6 for x in the expression.
a) 5x-9
5(6)-9
30-9
21
b) 2x-7
2(6) -7
12-7
5
c) 8x+5
8(6)+5
48+5
53
d) 4(x+3)
4(6+3)
4(9)
36
e) x²-(-4)
6²-(-4)
36+4
40
f) 3x²+1
3(6²)+1
3(36) +1
108+1
109
2) Solve
a) 54 = 3x
Divide both sides by 3.
54/3 = 3x/3
x = 18
b) x-9 = -3
Add 9 to both sides.
x-9+9 = -3+9
x = 6
c) x/7 = 140
Express the 140 over 1 and cross multiply.
x/7 = 140/1
x = 140×7
x = 980
d) x/8 = 72
Express the 72 over 1 and cross multiply.
x/8 =72/1
x = 72×8
x = 576