Solve P = a + b + c; for a
To solve for "a", we have to get rid of the "+ b + c" on the
right side so as to leave just the a on the right side:
P = a + b + c
To do that we add the opposite of + b and + c to both sides. The
opposites of + b is - b and the opposite of + c is - c, so we will add
that to both sides. To do that we have to skip some space between
the "P" and the equal sign "=" like this:
P = a + b + c
so we'll have room to insert the "- b - c", since there are no b or
c terms on the left to write those under. So now we put - b - c
undrneath both sides like this:
P = a + b + c
- b - c - b - c
Now we draw a line under that, like this:
P = a + b + c
- b - c - b - c
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Then below the line we add straight down in columns of
like terms. The + b and the - b cancel on t he right
and so do the + c and the - c, so we don't write anything
under them below the line on the right. You just bring
down everything else:
P = a + b + c
- b - c - b - c
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P - b - c = a
That's the answer. However, you might want to write the
right side on the left and the left side on the right so
that what you were solving for, the "a", is on the left of
the equal sign instead of the right:
a = P - b - c
Edwin
