Addition with Place Value: Finding Number Pairs That Sum to 98

To solve which addition exercise using tens and units results in 98, we will proceed with these steps:

• List the tens values we will consider: 10, 20, 30, 40, 50, 60, 70, 80, 90.
• For each tens value, subtract it from 98 to find the corresponding units needed.
• Verify which combination sums correctly to 98.

Let's examine each possibility:

- 10 + $x$ = 98 → $x = 98 - 10 = 88$ (not a unit, so invalid)
- 20 + $x$ = 98 → $x = 98 - 20 = 78$ (not a unit, so invalid)
- 30 + $x$ = 98 → $x = 98 - 30 = 68$ (not a unit, so invalid)
- 40 + $x$ = 98 → $x = 98 - 40 = 58$ (not a unit, so invalid)
- 50 + $x$ = 98 → $x = 98 - 50 = 48$ (not a unit, so invalid)
- 60 + $x$ = 98 → $x = 98 - 60 = 38$ (not a unit, so invalid)
- 70 + $x$ = 98 → $x = 98 - 70 = 28$ (not a unit, so invalid)
- 80 + $x$ = 98 → $x = 98 - 80 = 18$ (not a unit, so invalid)
- 90 + $x$ = 98 → $x = 98 - 90 = 8$ (This works, as 8 is a unit)

Thus, the addition exercise $90 + 8 = 98$ correctly adds to 98.

Therefore, the solution to the problem is: $90 + 8$.

The correct choice from the given options is: Choice 4: $90 + 8$