Mac - how do i make the letters smaller again?

[Shitemum]

I made the font far far too big on this borrowed mac - i pressed down the key next to the space bar, the one with the apple on it and a sort of squiggly square and at the same time the one with the star, the plus sign and the right-hand square bracket.
HELP!
What do i press to make them smaller again?

Please?
The letters are literally a cantimetre high on the screen - it is slowing up my MN-ing something awful!

try pressing the apple key again and the the minus key (to the left of the plus sign)...