There are 5 apple trees in an orchard, and the harvest of each tree this year is compared with last year as follows (increase in yield is positive, decrease in yield is negative). +45kg-50kg-30kg+60kg+20kg, how much has the total apple production increased or decreased this year compared to last year?
一个果园里有5棵苹果树，每棵树今年的收成与去年相比情况如下(增产为正，减产为负)．+45千克-50千克-30千克+60千克+20千克，今年苹果的总产量与去年相比，增产或减产多少？
<gadget id="calculator">45 + (-50) + (-30) + 60 + 20</gadget>
<output>45</output>

<result>45</result>