Explaining number bonds to 100

[disorganisedmummy]

My ds who is 7 and in yr 3 has a sheet of these for homework.He can do a far few without thinking but some he needs to work out but he can't remember what his teacher said and I'm struggling to explain it to him simply.
Can anyone help?

For multiples of 10, count on in tens to 100, so 30+?, would be 40,50,60,70,80,90,100-so 7 tens
For non multiples, count on to the next tens number and then in tens
so 43+? would be +7 to get to 50 and then 50 more to get to 100 so 57.

You could draw a number line to show the jumps!

would a number square help him visualise it?

100 is the same as 90 + 10, so the tens add up to 90, and the units add up to 10 (doesn't work for multiples of 10 though).

thanks everyone for your help.I'm so embarrassed as I asked ds's teacher how they do it,he explained it to me but he did it so quickly and in the middle of the playground with all the noise and to be honest I didn't quite get it.Maths really isn't my thing at all.
Ds has dyspraxia and aspergic traits so it's like pulling teeth doing homework with him at the best of times!!
Spanieleyes I did it a similar way though explained it appallingly!
CecinestpasunpipeThat is how I think ds's teacher explained it but I didn't really sink in-Thicko emoticion!