So the formula is
[tex]Interest= Principal*rate*time[/tex]
(Principal being the money he invested, time would be in years)
We let the principal of the first first investment be [tex]x[/tex]
this would make the principal of the second investment be [tex]x+12000[/tex]
The interest of the first investment would be
[tex]x* \frac{6}{100} *1= \frac{6x}{100} [/tex]
The interest of the second investment would then be
[tex](x+12000)* \frac{9}{100} *1= \frac{9x}{100} +120*9= \frac{9x}{100} +1080[/tex]
The sum of these two should be 4,830
[tex] \frac{6x}{100} +\frac{9x}{100} +1080=4830[/tex]
We combine like terms and subtract 1080 from both sides
[tex] \frac{15x}{100} =4830-1080=3750[/tex]
Multiply both sides by [tex] \frac{100}{15} [/tex]
[tex]x=3750* \frac{100}{15} =25000[/tex]
Therefore he invested P25,000 in the first investment and
P25,000+P12,000=P37,000 in the second investment.
