Can someone explain this to me? what i need to do?

Will all i see is this = 4x16=643x24=7264+72
                              =136136-15=121 

I Hope That Kinda Helped =D 

PART A
s = the number of packets of strawberry wafers ;
c = the number of packets of chocolate wafers ;
3 × s + 1 × c = 30 ;
s + c = 22 ;

PART B

The method of solving "by substitution" works by solving one of the equations (you choose which one) for one of the variables (you choose which one), and then plugging this back into the other equation, "substituting" for the chosen variable and solving for the other. Then you back-solve for the first variable.

c = 30 - 3s;
s + ( 30 - 3s ) = 22;
30 - 2s = 22;
30 - 22 = 2s;
8 = 2s;
s = 4 ;
c = 30 - 12 ;
c = 18 ;