Question

PAmelie solves the following system of equations x+y =20 and 3x-3y=30 which values of x and y satisfy this system of equations ?

Answer 1

we have that

x+y =20 ------> equation 1

and

3x-3y=30-----> divided by 3------> x-y=10-----> equation 2

let's add equation 1 and equation 2

x+y=20

x-y=10

-------------

2x=30--------> x=30/2------> x=15

x+y=20-----> y=20-x-----> y=20-15------> y=5

the solution of the system is

x=15

y=5

see the attached figure