Answer:
I think the answer is m= -1/3 b=7/3
Step-by-step explanation:
so first, you need to make equations using the info that the question gave. 
f(-2)= m(-2)+b f(4)= m(4)+b
 = -2m+b =4m+b
f(-2)= 3 f(4)= 1
-2m+b= 3 4m+b=1 -(2)
 b= 3+2m -(1)
substitute (1) into (2) : 4m+(3+2m)=1 
 4m+2m+3=1
 6m=1-3
 6m= -2
 m= -2/6
 m= -1/3
Substitute m= -1/3 into (2)
4(-1/3) + b=1
 -4/3 +b =1
b= 1+ 4/3
b= 7/3
Therefore, m= -1/3 b=7/3
and that's how you do it