The frog sits on the start number and has to reach the goal. Under the arch it says in how many hops it must do that, not one more and not one less.
Every hop is made with one of the cards. The card says how far it hops. You may play each card several times or not at all, and the order does not matter.
You are looking for how often each card is played. Together there must be exactly as many hops as the arch says.
For example from 2 to 28 in 4 hops with +10 and +3. Twice +10 gives 22, twice +3 gives 28. That is four hops, so it fits.
Try, adjust, check by adding. A card with minus makes the frog hop backward.
Example
For parents
What does this exercise practice?
Here a question sits behind the sum, one that is solved by trying and adjusting. The child does not work out one calculation but looks for a split that meets two conditions at once, the number of hops and the goal. It practices plus and minus up to 100, multiplying as repeated adding, and systematic trying. That there is exactly one solution makes the final check reliable.
Common pitfalls
The most common mistake is to reach only the goal and forget the number of hops. Whoever finds 22 plus 6 equals 28 but needs five hops for it has to start again. It helps to fix the number of hops first and then swap. The second stumbling block is a card that is not needed at all. Zero times is a valid answer too.
How to practice at home
Put a coin or a counter on a number of the hundred chart. One person names the goal and the number of hops, the other looks for the cards that fit. Two cards like +10 and +3 work for a start, and later cards with minus join in. Whoever finds a second solution has made a mistake, because there is only one.
Related: Number Sequence, Math Caterpillar