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20 should fit.

340 mm / 17mm = 20

80 balloons
8 x bunches = number of ballons.
bunches - dependent variable
balloons - independent variable

$90000-$15000=$75000 which was his old pay.
$90000/$75000 = 1.2
1.2-1=0.2
0.2*100=20%

First, expand the brackets:

-6p*7=6p-9+40-16p

Then simplify

-42p=-10p+31

Plus 10p to each side to get the 31 on its own