[Saul Good]

You're making this too hard. You don't have to blend all four. It's a lot easier to blend 2 and put it into a simple algebraic equation.

For example, you can use holdings 1 (x) and 3 (y).

x(8.5) + y(3.1) = 6.5% is your equation.

Now, you have to express x in terms of y. Because x+y= 100% (1.00) of your investment, x=1.00-y

Now, you re-write the equation with only the y variable:

(1-y)(8.5)+y(3.1)=6.5

Do the multiplication:

8.5-8.5y+3.1y=6.5

Simplify further

8.5-5.4y=6.5

Subtract 6.5 from both sides of the equation

2-5.4y=0

Add 5.4y to both sides

2=5.4y

Divide both sides by 5.4 to solve for y

.37=y

37% of your investment should be in y. The rest (1-y) should be in x.

Check your work: .37(.031)+.63(.085)=.065