When a battery of unknown emf is connected to a 50Ohm resist

When a battery of unknown emf is connected to a 5.0-Ohm resistor, the current in the circuit is 0.30 A. If the battery is now connected to an 8.0-f2 resistor, the current is 0.20 A. What are the emf of the battery and its internal resistance?

Solution

for a battery V=E-ir

for first connection E-.3r=5*.3

for second connection

E - ,2r=8*.2

solving we get r=1 ohm and e=1.8