Question 91417
5x+7y =b 

mx+y = 22 
Given that (-3,4) is a solution to the above system

Plugging in x = -3 and y = 4 in the first equation,

5(-3)+7(4) = b

==> -15+28 = b

==> 13 = b

So b = 13

Now m(-3) + 4 = 22

==> -3m + 4 = 22
==> -3m = 22-4
==> -3m = 18
==> m = 18/-3

==> m = -6

Good Luck!!!