F2L 27
The algorithm, how to recognise it and how to practise it without cheating.
Recommended algorithm
R U' R' U R U' R'7 moves · R and U only
Alternatives
R U' R' U2 R U2 R'7 moves · R and U onlyR U' R2 F R F'6 movesF' U2 F R U2 R'6 moves
How to recognise it
Corner in the slot with white facing you; the edge is on the right of the top layer, its side sticker matching the right centre.
Its inverse is another case
Do the 27 algorithm backwards, R U R' U' R U R', and you are solving 30.
That's why CubeDojo never scrambles 27 that way: it builds a random state with the case fixed, so you practise 27 and not 30.
Practise 27 now
Random-state scrambles, a timer and spaced review. Free, on the web and on your phone.