Substitution method
4a=4-b
4a=5-b
how to do this

A "solution" to this pair of equations is a pair of numbers, for 'a' and 'b',
that make the equations true statements.

I can tell you right now that this system of equations has no solution.
Here, let me show you why:

           4a = 4 - b
           4a = 5 - b

Subtract the bottom equation from the top one:

             0 = -1

Can you think of any numbers for 'a' and 'b' that could
make  0  equal to  -1 ?

I can't either.

There are no numbers for 'a' and 'b' that can make both equations true
statements.  That's just another way to say that the system of equations
has no solution.

Cytoplasm is a thick solution that fills each cell and is enclosed by the cell membrane. It is mainly composed of water, salts, and proteins. In eukaryotic cells, the cytoplasm includes all of the material inside the cell and outside of the nucleus.