Answer :
For the answer to be 130, change this....:
310 – 20 ÷ 2 × 5 + 13
....into this:
310 – 20 ÷ 2 × (5 + 13)
310 – 20 ÷ 2 × (5 + 13)
310 – 20 ÷ 2 × 18
310 - 10 x 18
310 - 180
= 130
310 – 20 ÷ 2 × 5 + 13
....into this:
310 – 20 ÷ 2 × (5 + 13)
310 – 20 ÷ 2 × (5 + 13)
310 – 20 ÷ 2 × 18
310 - 10 x 18
310 - 180
= 130