-
Solve for a and
check your solution.
-
And we have a plus
5 is equal to 54.
-
Now, all this is
saying is that we
-
have some numbers,
some variable a.
-
And if I add 5 to
it, I will get 54.
-
And you might be able
to do this in your head.
-
But we're going to do it a
little bit more systematically.
-
Because that'll be
helpful for you when we
-
do more complicated problems.
-
So in general, whenever you
have an equation like this,
-
we want to have the variable.
-
We want this a all by itself
on one side of the equation.
-
We want to isolate it.
-
It's already on
the left-hand side,
-
so let's try to get
rid of everything
-
else on the left-hand side.
-
Well, the only other thing
on the left-hand side
-
is this positive 5.
-
Well, the best way to get rid
of a plus 5, or a positive 5,
-
is to subtract 5.
-
So let's subtract 5.
-
But remember, this says
a plus 5 is equal to 54.
-
If we want the
equality to still hold,
-
anything we do to the left-hand
side of this equation,
-
we have to do to the right
side of the equation.
-
So we also have to
subtract 54 from the right.
-
So we have a plus 5 minus 5.
-
Well, that's just
going to be a plus 0.
-
Because if you add 5 and you
subtract 5, they cancel out.
-
So a plus 0 is just a.
-
And then 54 minus 5, that is 49.
-
And we're done.
-
We have solved for a.
-
A is equal to 49.
-
And now we can check it.
-
And we can check it by
just substituting 49 back
-
for a in our original equation.
-
So instead of writing a
plus 5 is equal to 54,
-
let's see if 49 plus
5 is equal to 54.
-
So we're just
substituting it back in.
-
49, 49 plus-- let me do that
in that same shade of green.
-
49 plus 5 is equal to 54.
-
We're trying to check this.
-
49 plus 5 is 54.
-
And that, indeed,
is equal to 54.
-
So it all checks out.
