Intersections
Intersections are the first natural technique people use when solving Sudoku, it's the first obvious method to find missing numbers.

Looking at Block5, where can the <7> go? The intersections of R5 & R6 limit the <7> to R4C4.


Looking at Block4. where can the <8> go? The intersections of R6, C2 & C3 limit the <8> to R4C1.
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