Here is another method:

Consider that solution is made of sugar and water:

Solution A: Total 1000gm (10% sugar)

1000= 900 (water) + 100 (Sugar)

Expected Solutin B: Total 1000gm (16% sugar)

1000= 840 (water) + 160 (Sugar)

Now, as said in the question 25% of the solution A is replaced with another solution, which means:

75% of the solution A in untouched and only 25% of the solution (250gm) is touched

Total Sugar in Solution B= 160 = (75% of sugar in solution A) + (sugar replaced in 25% of Solution A with a new solution)

Sugar replaced in 25% Solution A with a new solution = 160- 75 =85

Sugar in new solution: 85/250 = 340/1000 = 34% (Answer)

_________________

If you find my posts useful, Appreciate me with the kudos!! +1