Step 1 : Simplify both sides 
-5(6a+21)=-15
(-5)(6a)+(-5)(21)=-15
-30a-105=-15
Step 2 : Add 105 to both sides
-30a-105+105=-15+105
-30a=90
Step 3 : Divide both sides by -30
-30a=90
—————
-30 -30
a = -3
        
             
        
        
        
I'm not entirely sure but it should be (3/5) together. For pen the probability is (5/20) and for crayon is (12/20) add them equals (12/20) simply equals (3/5) HOPE IT HELPS
        
             
        
        
        
From general equation of a line;
y=mx+c
m=

m=

m=-1
y=-x+c 
Finding value of c;
using point (-2,0)
0=-(-2)+c
c=-2
y=-x-2
 
        
        
        
Answer:
20,800
Step-by-step explanation: