The sum of three numbers is 2100. the first number x is equal to the sum of the other two (y and z) which are equal to each other. what are the three numbers x, y and z

We will have a system of equations, and we are going to solve it by using substitution.

Let's make the equations.

x+y+z=2100

z+y=x

Since y and z are equal, I think it is easier for us to have them as one variable for now. Let the value of z and y be a.

These are the equations now.

x+2a=2100

2a=x

Since the second equation is giving the value of x, let it replace the value of x also in the first equation.

2a+2a=2100

4a=2100

2100:4 = 525

so, x and y equal 525. Let's put this in our original equation.

x+525+525=2100

x + 1,050 = 2,100

x = 1,050

So, x=1,050, y = 525 = z.