since S is a point on the line RT, therefore: RS+ST = RT 5y+5+3y+7 = 12y-20 separate the variables and solve to get thevalue of y as follows: 5+7+20 = 12y-3y-5y 32=4y y = 8
substitute in the equation of each line to get its length as follows: RS = 5y+5 = 5(8)+5 = 45 ST = 3y+7 = 3(8)+7 = 31 RT = 12y-20 = 12(8)-20 = 76
