1) Let's look at what we know and Create an equation:
Perimeter: 6x
Side A: x + 3
Side B: 2x + 4
Side C (Unknown): Let's call this 'a'.
Because you find the perimeter of a figure by adding the lengths of all its sides together, our equation would be (the parentheses are only there to help you visualize):
(X + 3) + (2x +4) + (a) = 6x
(Side A+Side B+Side C = Perimeter)
2) From here, we combine like terms:
3x + 7 + a = 6x
3) Isolate the variable in which we are solving for (a):
<u>a = 3x - 7</u>
Since we cannot simplify any further, the length of the missing side is <u>3x - 7</u>.
