Question

solve the problem:
100% - 9/10=
​​

Answer 1

100% =1
so
1 - 9/10
take the L.C.M and u can solve it easily

Answer 2

Recall: $$\Huge \text{%}=\dfrac{1}{100}$$

Answer 3

But it is not at all clear how the question wants the answer expressed as:

a fraction or a percent.

So, give both forms to be safe :-)