Question

4x+y=7, 16x+4y=28 solve the following equation by simultaneous method

Answer 1

I think you want substitution method
$y = 7 - 4x \\ 16x + 4(7 - 4x) = 28 \\ 16x + 28 - 16x = 28 \\ 28 = 28$
so we can see that value of x and y can't be evaluated.
now compare the coefficient
$\frac{4}{16} = \frac{1}{4} = \frac{7}{28} \\ \frac{1}{4} = \frac{1}{4} = \frac{1}{4}$
so these equation has infinitely many solution