Some care is needed at the end of the message but it starts clearly enough - 3,5,7 - assuming it's the misprints you're reading and not the corrections.
As mentioned earlier, ''appropriately highlighting'' should suggest how the search can be narrowed down.
For a really tedious grind try the Crossword Club's ''Checkerboard Challenge'' - grinding out over thirty sums (or over sixty if you have no faith in symmetry) before chucking them all away and inserting 8 eight letter words! Of course, these days, 60+ sums is many a Listener solver's idea of heaven.