# Problem with two unknowns

#### SILVER

##### New member
here is a problem i don't get:
2x+3y=7
-10x-3y=25
its a problem with two unknowns and the answer is x=-4, y=5. I started by adding the two together and got -12x=32 but when i divided that i got -0.37 and the answer ix=-4.HELP!

J

#### JeffM

##### Guest
SILVER said:
here is a problem i don't get:
2x+3y=7
-10x-3y=25
its a problem with two unknowns and the answer is x=-4, y=5. I started by adding the two together and got -12x=32 but when i divided that i got -0.37 and the answer ix=-4.HELP!
Does 2x + (-10x) = -12x?

I do wonder as well how you divided 32 by -12 and got -0.37.

Need to be more careful

#### SILVER

##### New member
2x+(-10x)=-32 does'nt it? when i divided 32 by -12 i got -2.66. How do i get -4?

#### Denis

##### Senior Member
SILVER said:
2x+(-10x)=-32 does'nt it? when i divided 32 by -12 i got -2.66. How do i get -4?
C'mon Silver...
2x + (-10x) = 32 : NOT -32
-8x = 32

#### Mrspi

##### Senior Member
SILVER said:
2x+(-10x)=-32 does'nt it? when i divided 32 by -12 i got -2.66. How do i get -4?
Why would you divide by -12? 2x + (-10x) is not -12x (it isn't 12x, either). It looks like you may need to review addition of signed numbers. Here's a website you can start with (there are many others available online):

http://www.purplemath.com/modules/negative2.htm

#### SILVER

##### New member
thanks,sorry careless mistake my brain does'nt seem to be working today