You add all of the numbers up each row and divide by how many there are so:
row one: if u add it all up it would be 10 then divide by how many there are
Answer:
the picture is not clear.
pls edit
Answer:

Step-by-step explanation:
Because
is being multiplied by S, we can divide
from both sides of the equation. This will give us:
÷
But, that looks a bit hectic. Instead of dividing, you can multiply by the reciprocal (which is essentially how to divide fractions). So, instead of
÷
, you get:
×
When multiplying fractions, remember you can just multiply straight across-- numerator x numerator, then denominator x denominator.
By doing that, you get the fraction 
cannot be simplified any more, so S=
is your answer :)
I hope this helps