x=2y 4x+2y=15?

Question

Algebra 1

Answer 1

x = 2y
4x + 2y = 15

Replace x with 2y in the second equation.
4(2y) + 2y = 15
8y + 2y = 15
10y = 15
y = 15/10
y = 3/2

Since x = 2y, then
x = 2(3/2)
x = 3

Answer: (3, 3/2)

Answer 2

solve the 2nd equation by substituting 2y for x.

4(2y) + 2y = 15
8y + 2y = 15
10y = 15
y = 15/10
y = 3/2

then solve the first equation

x = 2(3/2)
x = 3

Answer 3

*The problem isolates the x-variable in the 1st equation. You need to solve the variables by using the Substitution Method.

First: substitute "2y" with the x-variable in the 2nd equation...

4(2y) + 2y = 15
8y + 2y = 15
10y = 15

Sec: isolate the y-variable on one side by dividing both terms by "10"...

10y/10 = 15/10
y = 15/10 > *Simplify the fraction into lowest terms...
y = 3/2

Third: substitute "3/2" with the y-variable in the 1st equation...

x = 2(3/2)
x = (2*3)/2
x = 6/2
x = 3

Solution: (3, 3/2)

Answer 4

x=2y
4x+2y=15
substitute x for 2y
4x+x=15
5x=15
x=3
substitute 3 for x
3=2y
1.5=y
check
4*3 + 2(1.5) = 15
12 + 3 = 15
15=15

Answer 5

substitute x=2y in for all the x's
4(2y) + 2y=15
8y +2y=15
10y=15
y=3/2

then substitute 3/2 in for y
x=2(3/2)
x=3

solution is (3, 3/2)

Answer 6

x=2y <-- Eq 1
4x+2y=15 <-- Eq 2
Replace 2y in Eq2 with its equal x from Eq 1 getting:
4x + x = 15
5x = 15
x = 3
Now replace x in Eq 1 with 3 getting:
3 = 2y
3/2 = y