Question

x+y=15,x-y=3 find this solution in substitution method​

Answer 1

Step-by-step explanation:

$\sf x+y=15\dots\dots (1)$

$\sf x-y=3\dots\dots (2)$

• From eq (1)

$\qquad{:}\longrightarrow$$\sf x+y=15$

• Interchange sides and get y

$\qquad{:}\longrightarrow$$\sf y=15-x\dots\dots (3)$

• Substitute the value in eq (2)

$\qquad{:}\longrightarrow$$\sf x-y=3$

$\qquad{:}\longrightarrow$$\sf x-(15-x)=3$

$\qquad{:}\longrightarrow$$\sf x-15+x=3$

• Simplify

$\qquad{:}\longrightarrow$$\sf x+x-15=3$

$\qquad{:}\longrightarrow$$\sf 2x+15=3$

$\qquad{:}\longrightarrow$$\sf 2x=3-15$

$\qquad{:}\longrightarrow$$\sf 2x=-12$

$\qquad{:}\longrightarrow$$\sf x=\dfrac {-12}{3}$

$\qquad{:}\longrightarrow$$\bf x=-4$

• Substitute the value of x in eq(3)

$\qquad{:}\longrightarrow$$\sf y=15-x$

$\qquad{:}\longrightarrow$$\sf y=15-(-6)$

$\qquad{:}\longrightarrow$$\sf y=15+6$

$\qquad{:}\longrightarrow$$\bf y=21$

$\therefore{\underline{\boxed{\sf (x,y)=(-6,21)}}}$