Number Transformation: Adding 7 to the Units Digit of 900

To solve this problem, we'll follow these steps:

• Step 1: Identify the units digit of the number 900, which is 0.
• Step 2: Increase this digit by 7, resulting in $0 + 7 = 7$.
• Step 3: Form the new number by combining the unchanged hundreds and tens digits with the newly computed units digit.

Now, let's work through each step:
Step 1: The units digit of 900 is 0.
Step 2: Adding 7 to the units digit gives us 7.
Step 3: The remaining digits (hundreds and tens digits in 900) remain unchanged, so the number becomes 907.

Therefore, the number you are left with after increasing the units digit by 7 is $907$.