Answer:
159cm
Step-by-step explanation:
Sum of all sides of triangles is 180
so, 15+6=21
then 180-21=159
When you have a negative exponent, you move it to the other side of the fraction to make the exponent positive.
For example:
or 
or y²
So:

Your answer is B
1. i cant see it 2. g=68 h=112 3. i=111 j=69 4. m=37 k=37 l=143
6(2)+3y=15
12+3y=15
-12 -12
3y=3
3y/3 3/3
y=1
6(5)+3y=15
30+3y=15
-30 -30
3y=-15
3y/3 -15/3
y= -5