You can put this solution on YOUR website! There are no brackets. First you do multiplying and dividing, in the order of left to right in the problem. OK?
310 – 20 ÷ 2 × 5 + 13
310 – (20 ÷ 2) × 5 + 13
310 – 10 × 5 + 13
310 – (10 × 5) + 13
310 - 50 + 13
Now you just gather all of them up from left to right.
(310 - 50) + 13
= 260 + 13
= 273
(