What's the measure of the larger angle?

When 2 angles add up to = 180 degrees?

Well, can you tell me what supplementary means?

Yes that is right.

Supplementary is add to 180 and complementary is add to 90.

It is easy to remember which is which because 2 times 90 = 180 and 2 c's on top of one another, make an S.

Does that make sense?

anyway...

(4x+9)+(6x+3) = 180

4x+9+6x+3 =180

10x+12 =180

10x=168

x=16.8

I can see straight off that 6x +3 is going to be bigger  than 4x+9

so

the big one will be  6*16.8 +3 = 103.8 degrees   ( 103 degrees and 48 minutes)

check

the little one will be  4*16.8+9 = 76.2

103.8+76.2=180   great :))