Begin by setting up a ratio comparing the small triangle to the large triangle. Remember, combine the values of the parts of the sides given to find the total lengths of the sides:
Step-by-step explanation: You can find the value of x with a little knowledge about proportions between similar polygons. The sides with lengths relative to x are similar to each other meaning that you can use the proportion: x/3x+5 = 4/7 solve for x by cross multiplying and you will get the value of x.