Answer:
Step 2: 20x = 80 + 10x
Step-by-step explanation:
Step 1: 20x - 10 = 80 + 10x
Add 10 to each side
20x - 10+10 = 80+10 + 10x
20x = 90 + 10x
Step 2: 20x = 80 + 10x This has the first error
Step 3: 10x = 80
Step 4: x= 8
It affect the sum by being the higher number
19/25 * 100 = 1900/25 = 76 ....numbers greater then 15
7/50 * 100 = 700/50 = 14....numbers less then 15
100 - (76 + 14) = 100 - 90 = 10 <== numbers equal to 15