math
posted by Katherine .
A salesperson bought a caase of pens.On Monday, he sold 1/2 of the pens.On Tuesady, 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,

96

96 is a nice number, but it is not the answer to your problem.
Let x = total number of pens
.5x = Monday sales, which means that .5x remain.
30 = Tuesday sales
1/3(.5x30) = Wednesday sales
40 remained on Thursday
.5x  30  1/3 (.5x 30) = 40
Solve for x.
I hope this helps. Thanks for asking.