You need to get rid of the brackets first. The minus sign outside the bracket affects what's inside. It has the transforming power to turn pluses into minuses and minuses into pluses. So 8-a becomes -8+a when the brackets are removed, and the left hand side of the equation becomes 5a-8+a. We can add the a's together, so we get 6a-8. Now we need to collect the unknowns and the knowns together separately, if you see what I mean. First the unknowns: we've got 6a on the left and 4a on the right. When we cross over the equals sign we alter pluses to minus, minus to plus, divide to multiply, and multiply to divide. This applies to knowns and unknowns. Let's keep 6a on the left side of the equation and bring across the 4a from the right. 4a means +4a, but moving it across changes it to -4a, so we end up with just 2a on the left. We want to arrange the equation so that the unknowns are on one side and the knowns on the other. -10 is left on the right side and if we bring across to the right -8 from the left, it becomes +8 on the right, which becomes 8-10. If you have a problem thinking about the meaning of negative numbers, think of a thermometer and temperatures below freezing. What temperature do we get when we go 8 degrees warmer than -10? We get 2 degrees below zero, or -2. So 8-10 = -2. What have we got? 2a on the left and -2 on the right. The equals turns multiply into divide, so we divide the right by 2 because we used it to multiply on the left. That leaves us with a on the left and -1 on the right (the minus sign doesn't affect division). The answer then is a = -1. Let's check if that's right by substituting a = -1 in the original equation. We get -5 - (8 + 1) on the left, that's -14, and on the right we get -4 - 10, also -14. Remember, use the thermometer if you have problems grasping negatives. Negative is cooler, positive is warmer. So ten degrees below -4 takes us to 14 below, or -14. You may of course have no problem at all dealing with negatives, so I apologise if I insulted your intelligence. Anyway, you may need to explain it to someone else sometime...
