Find $1+2\cdot3-4+5.$
Next, I look for any multiplication or division. I see that there is a 2 times 3, so I do that first and replace it with 6. The expression becomes $1+6-4+5.$ Now, I only have addition and subtraction left, so I can do them from left to right. First, I add 1 and 6 and get 7. Then I subtract 4 from 7 and get 3. Finally, I add 5 to 3 and get 8. The expression simplifies to 8. 