Evaluate 13 + ab, when a = 2.5 and b = 3. a. 46.5 b. 20.5 c. 18.5 d. 19.5

When variables are touching, that means after plugging them in, we multiply.
So the equation becomes 13 + axb 
Lets fill a and b in:
13+(2.5)(3)
In the order of operations (or PEMDAS),we must multiply first. 
2.5 x 3 =7.5
Then the equation becomes:
13 + 7.5
No you just add to get your answer which is (B)20.5
Hope this helps!

Ibelieve 4mn because it’s like you’re combining them