You walk 2 miles in 1/ 2 hour. at that rate, how long will it take you to walk 3 miles?

The answer is:  "  mi. "  ;  or, write as:  " 0.75 mi. " .
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Write a proportion.  
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    ;

Solve for "x" , [ (in units of "h"; (hours) ] ; 

Note:  "Cross-multiply" ; 

Note:  Given (a/b) = (c/d) ;   → ad = ab ;   (b ≠ 0 ; d≠ 0) ; 

      →   2x = (0.5 * 3) ; 

      →   2x =  1.5  ; 

Divide each side of the equation by "2" ;
   to isolate "x" on one side of the equation; & to solve for "x" ;  

      →   2x / 2 = 1.5 / 2 ; 

to get:

       →   x = 1.5 / 2  = 15/20 = (15÷5) / (20÷5) = 3/4 ;

or:   →   x = 1.5 / 2 = 15/20 = (15*5) / (20*5) = 75/100 = 75 ÷ 100 = 0.75 . 
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 The answer is:  " mi. "  ;  or, write as:  " 0.75 mi. " .
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It is the answers of confederation