math substitution question.?

Question

I'm solving for both b and a
started with:
90+b+a=180
so:
b=90-a
so I substitute it in the original solution:
90+(90-a)+a=180
which goes to
(90-a)+a=90
that's where I get stuck

I can't remember how to keep going to solve for 'a' (it's been a couple years since my last math class)
you don't have to solve it out in the answer, but if you could just tell me what to do. I've been stuck on this for over an hour.
Thanks in advance

Answer 1

You can't solve for a and b with only one equation.

You need as many equations as you have variables.

if you solved for a it would be:
a=90-b

if you solved for b it would be:
b=90-a

You would need another equation to plug into in order to just have a number and not a variable in your answer.

But if the question is solve for a, then a=90-b is a valid answer.

Answer 2

For the equation 90 + b + a = 180,
you can only change the subject of the equation to
a = 90 - b or b = 90 - a.

There is no way for you to solve for a or b unless u have another equation with variables a and b.

Answer 3

You did well in getting an expression for b in terms of a, and you have the correct idea to substitute, but what you are missing is a second equation.
With 2 unknowns, a & b, you need 2 equations. Then you substitute into the 2nd equation not the original.
You will always get a 0=0 doing what you did.
look for another equation to be able to solve.
Otherwise, you have gone as far as possible with the given information. Good job!
Math isn't that hard, we sometimes make it more difficult that it is.

Answer 4

You can only solve for a in terms of b, similar to what you did above to solve for b. And as a result, a = 90 - b.

Answer 5

Hmm...this is a weird problem.
First off, when you have 90+(90-a)+a=180, the next step would be
180=180, not 90=90, because the a's cancel out. I'm kinda stumped as well though.

Answer 6

You can't solve for a and b with that equation.

Answer 7

a=45
b=45

This is so easy. It is probably an elementary school problem.