Question

Solve the system by substitution. Check your solution.

a-1.2b=-3
0.2b+0.6A=12



a.


(15, 15)


c.


(13, 12)




b.


(10, 12)


d.


(7, 9)

Answer 1

Dear NicoleAnn:
Your system,

a-1.2b=-3
0.2b+0.6A=12

could be made easier to solve by eliminating all the decimal fractions.
To accomplish this, multiply both equations by 10.

Then:
10a - 12b = -30
6a + 2b = 120

One of the easier ways to solve this would be to multiply the 2nd eq'n by 6, so that the b terms will be -12b and +12b respectively. Adding together the 2 equations will eliminate b and make it easy to solve for a.

Good luck!

Answer 2

@mathmale Thank you! I got 15,15, Is this corect?

Answer 3

Let's look at the process of checking your "solution" of a problem such as this one. You're wondering whether (15,15) is a solution.

Choose either one of the equations you originally posted here. For example, take

a-1.2b=-3

and substitute a=15 and b=15. Is the resulting equation true or false?

If true, you have a solution; if false, something's wrong.

You could check your sol'n in the other equation in exactly the same way.

Answer 4

If we have

a-1.2b=-3
0.2b+0.6A=12

I'd do the same thing as before: Multiply each equation by 10:

10a-12b=-30
6 a +2b = 120

Next, I'd multiply the 2nd equation by 6:

36a + 12 b = 720

and add the first equation to it:

36a + 12 b = 720
10a-12b=-30

The resulting equation is 46a=690, so a = 15.

Now we need to find b:

Substitute a = 15 into the 2nd equation: 10(15) -12b =-30

Solve the resulting equation for b.

Then check your "solution" again in the manner discussed above.

Suppose we get (15,15) again:

Substitute a=15 and b=15 into

36a + 12 b = 720. Is the equation then correct?

36(15) + 12(15) = 720 ??

Answer 5

So, in fewer words :) Yes, your answer is correct!!