Find the distance between points b and c. round to the nearest hundredth

Gregory draws a scale drawing of his room. the scale that he uses is 1 cm : 4 ft. on his drawing, the room is 3 centimeters long. which equation can be used to find the actual length of gregory's room?

Can anyone me with this question?

Si el duplo del mayor de dos numeros se divide entre el el triplo del menor, el cocient es 1 y el residuo 3, y si 8 veces el menor se divide por el mayor, el cociente es 5 y el residuo 1