Hello from MrBillDoesMath!
Answer:
x = 7/8
Discussion:
3[x + 3(4x – 5)] = 15x – 24 =>
3x + (3*3)(4x-5) = 15x - 24 =>
3x + 9*(4x) - (3*3)*5 = 15x - 24 =>
3x + 36x - 45 = 15x - 24 => (add 24 to each side)
3x + 36x - 45 + 45 = 15x - 24 + 45 =>
39x = 15x + 21 => (as 45-24 = 21)
39x-15x = 21 => (subtract 15x from both sides)
24x = 21 =>
x = 21/24 = -7/8
Regards,
MrB
P.S. I'll be on vacation from Friday, Dec 22 to Jan 2, 2019. Have a Great New Year!