This looks like scalar matrix multiplication. The idea here is to multiply the scalar 3 by each item inside the matrix.
Doing so leads to the answer [3   -12    15    -21]
Side note: I'm assuming the matrix given to you has 1 row and 4 columns.
 
        
             
        
        
        
15-(3•4) = m
m=how many markers Tim has left.
        
             
        
        
        
Answer:
70.7
Step-by-step explanation:
a2 +b2 = c2 
50^2 + 50^2 = c2 
c2 = 2500+2500 
c = 
 = 70.7
I hope im right!