Answer
$2.5$ pounds of green peppers and $0.5$ pounds of orange peppers.
Work Step by Step
Assume we bought $x$ pounds of green peppers. Then we bought $3-x$ pounds of orange peppers. Then our equation is: $x\cdot1+(3-x)4=4.5\\x+12-4x=4.5\\-3x=-7.5\\x=2.5$
Thus we bought $2.5$ pounds of green peppers and $0.5$ pounds of orange peppers.
