How many litres of pure antifreeze should be added to 5 litres of 30% antifreeze solution to create a 65% antifreeze solution?

0.65% of new amount=old amount of 30% plus amount of new
0.65(x+5)=5(0.3)+x
solve
distribute
0.65x+3.25=1.5+x
minus 1.5 from both sides
0.65x+1.75=x
minus 0.65x both sides
1.75=0.35x
divide both sides by 0.35
5=x

5 liters of pure should be added