Question

resolver:
4/2x+1 = 12/21

Answer 1

4/2x+1 = 12/21
Multiplicamos todo por 42
21(4)x + 42 = 12(2)
84x + 42 = 24
84x = -18
x= -18/84
x = -9/42
x = -3/14

Answer 2

A"         4/2x+1 = 12/21

            4(21)=12(2x+1)

              84=24x+12

                84-12=24x

               72=24x

                72/24=x

                  3=x

Espero que te sirva.....