Hi there!
We can find the perimeter of a triangle by adding all of its sides.
The perimeter of the triangle in the picture is therefore as follows:
[tex](7x + 8) + (9x - 4) + (6x + 6)[/tex]
Now do some simplification. First work out the parenthesis.
[tex]7x + 8 + 9x - 4 + 6x + 6[/tex]
Now rearrange our expression (in order to collect the terms later).
[tex]7x + 9x + 6x + 8 - 4 + 6[/tex]
Finally collect the terms.
[tex]22x + 10[/tex]
The second part of the question tells us that x equals 10. Therefore, we can plug in this value of x into our expression.
[tex]22(10) + 10 = 220 + 10 = 230[/tex]
Hence, the perimeter of the triangle is 230 millimetres.
~ Hope this helps you!
