Answer :
In this problem we have two incognitas, so we need to have two equations to solve the problem:
the first equation is the invest amound: (A is the amount invested in fund A, and B is the amound invested in the fund B)
[tex]A=3B[/tex]And the second equation is going to be the total profit:
[tex]A0.8+B0.6=1800[/tex]Now we can replace the equation 1 in the second one:
[tex]3B(0.8)+B0.6=1800[/tex]And finally we solve for B:
[tex]\begin{gathered} 2.4B+0.6B=1800 \\ B(2.4+0.6)=1800 \\ B(3)=1800 \\ B=\frac{1800}{3} \\ B=600 \end{gathered}[/tex]