Question

if x+y =10 and x=z so hat z+y=10

Answer 1

Yes this statement is correct..

x+y=10 ---(1)

and

x=z

so simply replace x by z in eq(1).

then we get-

z+y=10.

Answer 2

eq 1 se x=10- y
and we put it in eq. 3
10- y + y=10
it gives us0=0 so it is one eq. also.