Do 340 ✖️0.20, and you'll get 68. Since that's 20% of 340, do 340 ➖ 68 and you'll get your final answer.
Answer:
D
A = 1, B = 1, C = -8, D = 0, and
The mistake is that they subtracted 21 instead of adding it. you would have had to added 21 to the left side to cancel it out and added 21 to the right side to get p= 55