4g+13 is the same as 13+4g when using the commutative property.
Specifically, it is the commutative property of addition.
This says we can add two numbers in any order. For example, 7+9 = 16 and 9+7 = 16 as well. So 7+9 = 9+7. More generally, x+y = y+x for any pair of real numbers for x and y.
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If we plug in g = 10, then
4g+13 = 4*10+13 = 40+13 = 53
and
13+4g = 13+4*10 = 13 + 40 = 53
We get 53 both times, so 4g+13 = 13+4g is confirmed to be true when g = 10
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Repeat for g = 2
4g+13 = 4*2+13 = 8+13 = 21
and
13+4g = 13+4*2 = 13+8 = 21
both results are the same, so 4g+13 = 13+4g works for g = 2 as well.
You should find it works for any number you pick for g.
