Question 1128087
An investment of ​$106,000 was made by a business club.

 The investment was split into three parts and lasted for one year.

 The first part of the investment earned​ 8% interest, Let investment be x

 the second​ 6%,  let investment be y

 and the third​ 9%. let investment be z


x+y+z =106000----------------------------------------(1)

 Total interest from the investments was $8100. 
8%x+6%y+9%z = 8100 -------------------------------(2)


The interest from the first investment was 4 times the interest from the second. 
8%x= 4*6%y
8x=24y
x=3y
substitute x=3y in (1)
x+y+z=106000
4y+z=106000  ----------------------------(3)

8%x+6%y+9%z = 8100
substitute x=3y

8%(3y)+6%y+9%z=8100
Multiply by 100
24y +6y +9z= 810000
30y+9z= 810000 --------------------------(4)
multiply (3)by 9 and subtract (4)

36y+9z=954000
30y+9z= 810000

6y= 144000
y= 24000

x=3y
x= 72000

106000 -96000 = 10000 =z

The first part of the investment earned​ 8% interest. $72,000

 the second​ 6%,  investment  . $24,000

 and the third​ 9%. investment $ 10,000

Check

72000*8%+24000*6%+9%*10000 =8100