First, you need to get rid of the parenthesis, so you need to distribute:
12(–1.4m + 0.4) = m + 0.2
-16.8m + 4.8 = m +0.2
Then subtract both sides by m:
-16.8m - m + 4.8 = m +0.2 - m
-17.8m + 4.8 = 0.2
Subtract both sides by 4.8:
-17.8m + 4.8 - 4.8 = 0.2 - 4.8
-17.8m = -4.6
Now, divide both sides by -17.8:
-17.8m/-17.8 = -4.6/-17.8
m ≈ 0.258
