Question

If $3x+5y=9$ and $5x+3y=7$ then what is the value of $x+y$ ?

Answer 1

3x+5y=9-----(1)

5x+3y=7-----(2)

multiplying eq(1) by 5 & eq(2) by 3 we get

15x+25y=45

-15x $\pm$ 9y= - 21

_____________

16y=24

y=$\frac{24}{16}=\frac{3}{2}$

$[y=\frac{3}{2}]$ and $x=\frac{9-5x\frac{3}{2}}{3}=\frac{-1}{2}$

Hence$[x=\frac{1}{2}]$& $[y=\frac{3}{2}]$

so $x+y=\frac{1}{2}+\frac{3}{2}$=2