1. The sum of a number and ten.

X+10

X+10
Explanation:
Break down the information given to you to try and identify what the algebraic expression must looks like. You know that you're dealing with
a sum
→
this means that you are adding something, so you're going to use the
+
sign;

of a number
→
this means that you're dealing with a variable. The most common notation for a variable is
x
.

and 10
→
this is simply an integer that must appear in the algebraic expression along the variable
x
.

So, put all this together to get
x
+
10
You're adding an unknown number,
x
, to an integer,
10