4,000 is invested at 3% interest how much money must be invested at 5% interest so that the total interest from the two investments is $195 after a year

Money 1: $4,000 is invested at 3% interest
Interest 1: I1=4,000*3%=4,000*3/100→I1=120

Money 2: x invested at 5% interest
Interest 2: I2=x*5%=x*5/100→I2=0.05x

The total interest from the two investments is $195 after a year
I1+I2=195
120+0.05x=195

Solving for x:
120+0.05x-120=195-120
0.05x=75
0.05x/0.05=75/0.05
x=1,500

$1,500 must be invested at 5% interest so that the total interest from the two investments is $195 after a year

The following relation is not a function