1.
ax-b=c, for x add b to both sides
ax = b + c divide both sides by
x = [ b + c ] / a
2.
15x+1=y, for x subtract 1 from both sides
15x = y - 1 divide both sides by 15
x = [ y - 1 ] / 15
3.
(x+f)+2=j, for x subtract 2 from both sides
x + f = j - 2 subtract f from both sides
x = j - 2 - f