Question

How do you solve this type of problem?

Answer 1

It's a fact that the sum of the angles of a triangle add up to 180º.

So, 55º + 85º + (3x+4)º = 180º.

That's the equation you need to solve:

55 + 85 + 3x+4 = 180 (combine like terms)

144 + 3x = 180 (subtract 144 from both sides)

3x = 36 (divide both sides by 3)

x = 12 (you've got x)