Firstly, you've got to expand the brackets, this becomes;
8a-4= -10a+ 50
You've then got to eliminate the -10a and you do this by adding 10a to both sides,
This then becomes 18a-4=50
You've then got to add 4, to eliminate this, which then becomes 18a=54
You've then got to divide both sides by 18, and this becomes 3.
Therefor, a=3
Hope this helps :)
The answer is D you move the decimal over 1 then add 2 0
