An antique clock costs €80. Its price is increased by 45%. What is it now worth?

To calculate the percentage increase:
First: work out the difference (increase) between the two numbers you are comparing.

Increase = New Number - Original Number

Then: divide the increase by the original number and multiply the answer by 100.

% increase = Increase ÷ Original Number × 100.

If your answer is a negative number, then this is a percentage decrease.

To calculate percentage decrease:
First: work out the difference (decrease) between the two numbers you are comparing.

Decrease = Original Number - New Number

Then: divide the decrease by the original number and multiply the answer by 100.

% Decrease = Decrease ÷ Original Number × 100

If your answer is a negative number, then this is a percentage increase.

If you wish to calculate the percentage increase or decrease of several numbers then we recommend using the first formula. Positive values indicate a percentage increase whereas negative values indicate percentage decrease.

Read more at: https://www.skillsyouneed.com/num/percent-change.html