SOLUTION: Please help me with this problem I don't understand how to do this. Thank you. Q:find the value of x. 30/48= 15/x+9

Question 78341: Please help me with this problem I don't understand how to do this. Thank you. Q:find the value of x.

30/48= 15/x+9
Answer by bucky(2189) (Show Source): You can put this solution on YOUR website!
Given:
.

.
A simple rule that you can remember in working proportion problems is that you can begin to
solve them by cross-multiplying and then setting the two products equal.
.
Multiply the numerator of the left side times the denominator of the right side. Then
multiply the denominator of the left side times the numerator of the right side. Finally,
set these two products equal.
.
[Note that you can imagine a line connecting the numerator on the left with the denominator
on the right, and then imagine another line connecting the denominator on the left with
the numerator on the right. These two lines cross ... and since each line connects
the numbers to be multiplied they are referred to as cross products.]
.
Doing the cross products for this proportion and setting them equal results in:
.

.
Doing the distributed multiplication of the left side gives:
.

.
(the 270 comes from 30*9}. Then multiply the right side 48*15 and the equation becomes:
.

.
Now just solve like you would an equation. Isolate the term on the left that contains
the "x" by subtracting 270 from the left side. But when you do that you have to also
subtract 270 from the right side. This process is:
.

.
and doing the subtraction results in:
.

.
Solve for x by dividing by 30, the multiplier of x to get:
.

.
The answer to the problem is x = 15. Check it by returning to the original problem and
substituting 15 for x. When you do that you get:
.

.
Add the terms in the parentheses and the equation becomes:
.

.
Now divide 30 by 48 and see if you get the same answer as you do when you divide 15 by 24.
You will, and this shows that when you use 15 for x, the equation will be true ... both
sides will be equal.
.
Hope this helps to expand your knowledge of how to solve proportions ... (a proportion
occurs when two ratios are set equal).
.
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