2*(3+x)-5
6+2x-5
1+2x
2*(3 + x) - 5
= 2*3 + 2*x - 5 <--- multiply the thing inside the bracket by 2
= 6 + 2x - 5 <--- 2*3, basic math.
= 2x + 6 - 5 <--- rearrange.
= 2x + 1 <--- 6 - 5, basic math again.