what are a and b is a+3b=-3 and 2b=a-12.

Given the equations:

a + 3b =
-3 ..............(1)

2b = a
-12

==> -a+2b =
-12 ............(2)

We have a system of two equations and
two variables.

Then, we will use the elimination method to
find a and b.

==> We will add (1) +
(2).

==> 5b= -15

Now we
will divide by 5.

==> b = -15/5 =
-3

==> b= -3

Now we
will substitute into (1) to find a.

==> a + 3b =
-3

==> a + 3(-3) =
-3

==> a -9 =
-3

==> a = 9-3 =
6

==> a = 6

Then, the
answer is:

a = 6   and   b =
-3