The first thing we must realise is that there are brackets in this equation and thus this has to be dealt with. We expand out the brackets on the left side by multiplying 7 by x and 2 to obtain '7x+14'. We now have the equation '7x+14 = 5x +21'. We have to collect the x terms on one side, preferably the left hand side, and the other constants on the other side. Subtracting 5x from both sides, we get '2x+14 = 21'. We repeat the same by subtracting 14 from both sides to get '2x = 7'. To find the solution to this equation we have to find out the value of x and thus if we divide both sides by 2 we get the final solution, x=3.5 or 7/2