Make b the subject of the formula a = 3 - 2b

So this question wants you to rearrange the formula so that b is on its own on one side of the equals sign. As its a formula and not asking for the value of the equation you don't have to worry about solving a or b, just rearranging it so b is on its own. So the first thing to do is remove the 3 which is being added to b, this can be done by subtracting 3 from both sides of the equation. This would give 3 - 2b - 3 = a - 3 which leaves you with -2b = a - 3. Now you're just left with the minus 2, which is multiplied by b. Therefore you can remove that by dividing both sides by minus two. This would give you -2b/-2 = a - 3/-2. The minus 2 cancel out on the left side leaving just b. However the right side can also be simplified because you can remove the minus from the division as it changes the positive and negative values for a and -3 such that b = -(a -3)/2. You can expand this bracket to give b = 3 -a /2.