^{I need to solve for "a" I tried to solve it and I ended up with (2 1/2)/2=a. I don't know if that is right or not and even if it is I don't know what to do next.}

- 3/2 = - 2a +1

cross multiplyimg both side we'd have

( -3 * 1) = 2 ( -2a + 1 )

which gives;

-3 = -4a + 2

moves 2 over the equality sign and it become -2

we'd then have

-3 - 2 = -4a

which gives

-5 = -4a

solving for a, divide both sides by -4

we'd have

-5 / -4 = -4a / -4

giving

5/4 = a