Question

If 5 x + 3y = 20 and 3 x + 5 y = 12 then what is the value of x+ y

Answer 1

$\sf\huge\bold{\underline{\underline{{Solution}}}}$

The above equation can be solved through elimination method :

$\sf \longmapsto5x + 3y = 20 - - (1) \times 3$

$\sf \longmapsto3x + 5y = 12 - - (2) \times 5$

New Equation obtained:

$\sf \longmapsto15x + 9y = 60$

$\sf \longmapsto15x + 25y = 60$

=>15 x+9y= 60

=>15x+25y=60

=>$(-)\:(-)=(-)$

_______________

-16y=0

y=0

Put y's value into equation 1

=>5x+3y=20

=>5x+3(0)=20

=>5x+0=20

=>5x=20

=>x=20÷5

=>x=4

x=4

CHECK:

=>5x+3y=20

=>5x+3(0)

=>5×4=20

Now,we have to find the value of x+y

$\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$=>4+0=4

Therefore,the value of x+y is 4 .

Answer 2

Given:

x+y=5, and

x=3

Substituting the value of x in the given equation, we get

3+y=5

⇒y=2