Is this two separate problems?
If so: 6(7+5x) = 3126= 42 + 30x = 3126; subtract 42 from both sides: 30x = 3084; divide both sides by 30 and x= 12 24/30 or 12 4/5.
(7 +5x) =312; subtract 7 from both sides: 5x= 305; divide both sides by 5 and you get x = 61.
