You would move over the -2 making the equation look like this 4x>3x+7. Then move the 3x to the other side of the equation making it look like this 1x>7. Thus the answer is x>7.
I would have each block be 1/6 of a yard
You could technically have any value you want, but for me 1/6 is easiest because 1/2 and 1/3 will scale up to this like so
1/2 = (1/2)*(3/3) = 3/6
1/3 = (1/3)*(2/2) = 2/6
The diagram below might help if you're still stuck on why I picked 1/6.
£350 because 420/6 is 70 and 70*5 is 350