How did the temperature change if: at first it increased by 5% and then increased by 20%

26%

Step-by-step explanation:

There was not a given number, so I chose 100.

It was increased by 5%, so now our number is 105.

It is increased by 20% now.

20% of 105 is 21.

Now I add 21 to 105 and get 126.

126-100= 26,

so it was increased by 26%