5 + 2n = 7
2n = 2
n = 2/1
n = 1
Hope i helped :)
One last tip, if your given any harder questions on this topic you can sometimes get a pair of equations where there are not a pair of equal values. To solve this you must create a pair of equal values, for example if the origional equations are:
2x + 3y = 8
x + 2y = 5
You multiply everything in the first equation by 2, so that you get 6y, and everything on the bottom equation by 3 so you also get 6 y, which gives the pair:
4x + 6y = 16 (remember to times everything, on both sides)
3x + 6y = 15
You can then solve this pair of equations normally.
Hope I help, I never use to understand this :)