Acompany invested 25000 at an annual simple interest rate of 4.1% how much additional money must be invested at an annual simple interest rate of 5.6% so that the total annual interest earned will be 4.8% of the total investment

We take interest+interest+interest to equal interest
0.041=4.1%(25000) the amount invested+0.056=interest they want=0.048 the total amount wanting to earn 4.8% and x is the added money to invest.
0.041(25000)+0.056x=0.048(25000+x)
1025+0.056x=1200+0.048x
subtract the 0.048 from both sides
1025+0.008x=1200+x
Subtract the 1025 from both sides
1025-1025+0.008=1200-1025+x
0.008x=175+x
Now divide 175 by 0.008
x=21,875

Maybe the answer is 20mm. all i really did was just multiply, which is obvious.