Answer :
hopefully this helps you and gives you insight in how to solve the problems from now on (:
= $11.8 + (2012-1997)([$11.8-$7.4][1997-1990])
= $11.8 + 5 ($4.4/7)
= $11.8 4/5 + $22/7
= $59/5 + $22/7
= $413/35 + $110/35
= $523/35 or $14 33/35
answer : SALES IN 2012 WOULD BE $14 33/35 BILLION OR $14.9 3/7