How do you solve the proportion #(x+1)/(x +3) = 15/21 #? Algebra Rational Equations and Functions Rational Equations Using Proportions 1 Answer Anees Apr 29, 2015 #x=4# Solution #(x+1)/(x+3)=15/21# #(x+1)(21)=15(x+3)# #21x+21=15x+45# #21x-15x=45-21# #6x=24# #x=24/6# #x=4# Answer link Related questions How do you solve proportions? What is Rational Equations Using Proportions? How do you solve #\frac{2x}{x+4}=\frac{5}{x}#? How do you use cross multiplication to solve #\frac{2}{x+3}-\frac{1}{x+4}=0#? What is cross multiplication? How do you solve #\frac{3x^2+2x-1}{x^2-1}=-2# using cross multiplication? How do you solve #\frac{7x}{x-5}=\frac{x+3}{x}#? How do you cross multiply #\frac{4x}{x+2}=\frac{5}{9}#? How do you solve #4/(x-3)=4#? How do you find fractional notation for the ratio 1.6 to 9.8? See all questions in Rational Equations Using Proportions Impact of this question 4031 views around the world You can reuse this answer Creative Commons License