Answer: 33.33%
If suppose sp is 100% (assume)
Then gain % is 25%..
Then subtract it from sp we will get cp i.e 100-25=75%.
We know two basic formulas %gain=(gain/cp)*100 . or %loss=(loss/cp)*100.
So %gain=(25/75)*100=33.33
-Balue
Let present ages be 'a' and 'b'.after 10 yrs A's age will be a+10and that of B will be b+10age of B before 10 yrs = b-10so given condition is a+10=2(b-10)second condition is a-b=9solving these two equations we getb=39so after 10 yrs B's age will be 39+10=49