A 15% percent markup means that the typewriter cost was increased by 15%, or 0.15 by moving the decimal 2 places to the left. If the original price was x, and 15% of it is 0.15*x, we can add them up to get 1.15*x=129.95. Dividing both sides by 1.15, we get x=113 dollars
Sale price=129.95 Mark up=15% x=at cost price to ABC Set up proportion: 129.95 x --------- = ---------- (Got 1 from 100% which is the cost to ABC and 1.15 from 100% 1.15 1 +15% which is the cost to customer then changed to decimal form.) Cross multiply 129.95=1.15x 129.95/1.15=1.15x/1.15 113=x Cost to ABC is $113