Step-by-step explanation:
9) given
[tex]12x = 4(x + 2) + 20 \\ 12x = 4x + 8 + 20 \\ 8x = 28 \\ x = 28 \div 8 \\ = 3.5[/tex]
10)standard form equation: y=mx+c
where m = slope and c = y-intercept
given m = 8, c = 12,
equation of line :
[tex]y = 8x + 12[/tex]