Here we want to have x on one side of equation so,
we put number 5 on right side of equation:
abx=5
then we divide both sides by ab to obtain x on left side:
Result:
x=<u />
They want to make a total of $1200.
55*10=550
55*8=440
440-550=990
1200-990=210
210/35=6
So they should sell the other plants for $6 each.