Question

calcule "x":x+3/4=x+9/7

Answer 1

$\frac{x+3}{4} = \frac{x+9}{7} =\ \textgreater \ 7x+21=4x+36 =\ \textgreater \ 3x=15 =\ \textgreater \ x= \frac{15}{3}=5$

Answer 2

x + 3          x + 9
---------   = ----------  
   4                 7

7.(x + 3) = 4.(x + 9)
7x + 21 = 4x + 36
7x - 4x = 36 - 21
3x = 15
x = 15/3
x = 5