What will be my new age?

Relevant wiki: Setting Up Equations

let $M$ be my age today and $A$ be the age of Ana today

the equations are:

$M=15+A$ $\implies$ $\text{today}$

$M-5=2(A-5)$ $\implies$ $\text{five years ago}$

Substituting the first equation to the second equation, we get

$15+A-5=2A-10$ $\implies$ $A=20$

It follows that,

$M=15+A=15+20=35$

Finally,

$M+1=$ $\boxed{\color{#D61F06}36}$