The perimeter of a triangle is 7a - 11b. If two of its sides are 2a + b and a - 9b, what is the third side? Algebra Expressions, Equations, and Functions Problem-Solving Models 1 Answer Tony B Mar 19, 2018 #4a-color(white)("d")3b # Explanation: #2a+color(white)("d")b# #ul(color(white)("d")a-9b larr" Add"# #color(red)(3a-8b) larr" Sum of 2 sides"# #color(white)("d")# #7a-11b larr" Sum of all 3 sides"# #ul(color(red)(3a-color(white)("d")8b)larr" Subtract")# #4a-color(white)("d")3b larr" Remaining side"# Answer link Related questions What are the steps to solving a word problem? Where do I start when I'm trying to solve a word problem? How do you check a solution to a problem? What are the different strategies used to solve a word problem? What is the best method of determining the cost of downloading 26 movies, if it cost $2.25 to... How do you solve word problems involving percents? What are commonly used math terms that translates to addition, subtraction, multiplication, and division? How much pure antifreeze should be added to 3 gallons of a 30 percent antifreeze solution to get... How would you use equations to calculate the age of Al given that Al's father is 45 and he is 15... How do you solve #x=(y-1)/(y+1)# for y? See all questions in Problem-Solving Models Impact of this question 11771 views around the world You can reuse this answer Creative Commons License