We start with “a number” — call it x, or maybe n — and work outward.
We have “twice a number”: 2
2
n
We have “half the number”: 12
1
2
n
, or 2
n
2
We have “the sum of” [the preceding two expressions]: 2+12
2
n
+
1
2
n
Aaand “is 10”: =10
=
10
Put it all together, and we get: 2+12=10
2
n
+
1
2
n
=
10
⟹2.5=10⟹=4
I hope it works