How to transpose this formula L=4a-8r+2pie r making a as subject?

L=4a-8r+2pie r

Move everything to the left side of the equation that doesn't have (a) in it. Do this by adding 8r to both sides, and subtracting 2(pie)(r) from both sides to get:

L + 8r - 2(pie)(r) = 4a.

Divide both sides by a to get

L/4 + 2r - (1/4)(pie)(r) = a

A four- cylinder four stroke - engine has a bore of 85 mm and a stroke of 125mm, the engine develops 40 kw at 2400rev./min