To solve the problem, let's define \( c \) as the number of cans already on the shelf. According to the problem, the shelf can hold a total of 58 cans, and since Alexei can still put 39 cans on the shelf, this means that there are currently \( c \) cans on the shelf and there is space for 39 more cans.
The correct equation that expresses this relationship is:
\[ c + 39 = 58 \]
Now, we can solve for \( c \):
- Subtract 39 from both sides: \[ c = 58 - 39 \]
- Calculate the right side: \[ c = 19 \]
Thus, the correct equation is \( c + 39 = 58 \) and the answer is \( 19 \).
So the correct response is:
c + 39 = 58 and 19.