Write a problem that can be solved with a bar model that shows equal groups of liters. then solve the problem.

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.

if the rectangular pool has a area of 192 square ft. and length of 15 ft. you must divide 15 into 192. 192 ÷ 15 = about 13 ft.