First add the ratio numbers together: 5+3+2=10.
Then, take each separate number and divide by the sum: 5/10=1/2; 3/10; 2/10=1/5.
Apply these fractions to the amount R50000: R25000; R15000; R10000. These are the amounts each sister receives (note that 1/10 is R5000, so just multiply this by 5, 3 and 2).