A salesperson bought a case of pens. On Monday, he sold ½ of the pens. On Tuesday, he sold 30 more. On Wednesday, he sold 1/3 of the pens that were left. On Thursday, he sold the remaining 40 pens. How many pens were originally in the case?
+37157 p= total number of pens originally
sell 1/2 then 1/2 remain
p - 1/2 p -30 = pens after Tuesday
(p- 1/2 p - 30) 2/3 = pens after Wednesday and this = 40 that were sold on Thursday
(p-1/2p-30)2/3 = 40
(1/2 p-30)(2/3) = 40
1/3 p - 20 = 40
1/3 p = 60
p = 180 pens
