We know one angle is 12 degrees.

That leaves 168 degrees.

One angle is five times larger than the other or 168 divided by six sections. (we have one known section plus five unknown sections)

168/6 = 28

So one angle (A) is 12 degrees

the second angle (B) is 28 degrees

the third angle (C) is 168 minus 28 or 140 degrees.

Prove your answer:

5 times 28 equals 140

140 + 28 + 12 = 180

So, lets call these 3 angles a,b & c.

So we know that a + b + c =180.

they tell you that the first angle is 12 and that the second angle is 5 times the size of the third. we can arrange this as follows.

a = 12

b = 5*c

c = ? we don’t know yet

rewrite the equation

12 + 5c + c = 180 because we b =5c so we substituted it so we have fewer letters to deal with.

now simplify

12 + 6c =180

6c = 180 -12

6c = 168

c = 168/6

c = 28 degrees

the answer is 28 but don’t take it by faith. lets substitude back into the equation just to make sure

12 + 5(28) + 28 =180

12 + 140 + 28 =180

152 +28 =180

180 = 180 checked

2nd = 140 degrees

3rd = 28 degrees

a = 12

b + c = 168

b = 5c

so 5c + c = 168 = 6c

c = 28 degrees