SOLUTION: Find x to make the ratios form a proportion With checking 1.) 12 : 7 = x : 21 2.) 3/2 : 4/3 = x : 7/6 3.) x : 12 = 5 : 8 4.) 7 : 9 = 49 : x

Question 1061377: Find x to make the ratios form a proportion
With checking
1.) 12 : 7 = x : 21
2.) 3/2 : 4/3 = x : 7/6
3.) x : 12 = 5 : 8
4.) 7 : 9 = 49 : x
Answer by HelpfulBro(2) (Show Source): You can put this solution on YOUR website!
1. 12 : 7 = x : 21 can also be written as fractions:
12/7 = x/21
Next step is to cross multiply and solve for x:
( 12 * 21 ) = ( 7 * x)
252 = 7x
To isolate x, we divide 7 to both sides of the equation:
252/7 = 7x/7
x=36
TO CHECK, WE SUBSTITUTE THE VALUE OF X IN THE PROBLEM:
12/7 = 36/21
Once again, we cross multiply.
12*21 = 7 * 36
252 = 252

SAME PROCESS APPLIES TO ALL THE OTHER PROBLEMS.
2.) 3/2 : 4/3 = x : 7/6
for this number, we'll have to simplify them first.
3/2 : 4/3 would be simplified as 9/8; as for
x : 7/6 , it would be 6x/7
now that they're simplified, we can now write our eqn as:
9/8 = 6x/7
We solve the problem applying the same process we did on number 1
9/8 = 6x/7
63 = 48 x
63/48 = x
21/16 = x
CHECKING:
3/2 : 4/3 = x : 7/6
9/8 = 6x/7
9/8 = [6*(21/16)] / 7
9/8 = (63/8) / 7
9/8 = 63/56
9/8 = 9/8
72 = 72
3.) x : 12 = 5 : 8
X/12 = 5/8
8X = 12 * 5
8X = 60
X = 15/2
CHECKING:
(15/2)/12 = 5 / 8
15 / 24 = 5 / 8
8*15 = 24*5
120 = 120

4) 7 : 9 = 49 : x
7/9 = 49/X
7x = 441
x = 63
CHECKING:
7/9 = 49/63
7*63 = 9*49
441 = 441

Hope this helps xD

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