Jacob bought two types of pens: blue pens that cost 0.60 each and red pens that each cost d times as much as a blue pen. If the cost of 3 blue pens and 6 red pens was $10.80, what is the value of d?

There are no answer choices for this questions as it was free responce but i got my answer as 1.5 and the right answer was 2.5.

My work:

0.6(3)+d(6)=10.8

d=1.5

BLANK Aug 7, 2020