Simple interest formula:
[tex]I=P\cdot r\cdot t[/tex]I is the interest earned
P is the principal
r is the interest rate (in decimals)
t is the time (in years)
For the given situation:
[tex]\begin{gathered} P=3,000 \\ r=\frac{1.2}{100}=0.012 \\ t=3 \\ \\ I=3,000\cdot0.012\cdot3 \\ I=108 \end{gathered}[/tex]Then, Bertalan will earn $108 in interest in 3 years