In triangle ABC, the size of angle B is 5 times the size of angle A, and the size of angle C is 7 less than 4 times the size of angle A

It sounds like everything is being described in reference to angle A, so a good starting point is to pick a variable to represent the measure of angle A. I'm going to use "a" for that.

Next, I'm going to take the verbal descriptions in the problem and "translate" them into "math language". They say angle B is 5 times angle A, so that means the measure of angle B is actually 5a. The size of angle C is 5 degrees less than 4 times the size of A, so that translates to 4a-5.

We now know the following:

Angle A: a
Angle B: 5a
Angle C: 4a-5

Now, to find the value of a, we need to remember that all the angles in a triangle add up to 180 degrees.

So we have: a+5a+4a-5 = 180

We can solve that equation by combining like terms to get: 10a-5=180

We can add 5 to both sides: 10a =185

And divide by 10: a = 18.5

That tells us the measure of angle A! (It's 18.5 degrees). Now we can go back and find B by multiplying A by 5. We get 92.5 degrees for that.

Finally, we can find C by taking 4*18.5-5. We get 69 degrees for that.

One last thing-- let's check that they really do add up to 180! 69+92.5+18.5 = 180. Yep!

Hope that helps you!!