If these are Plain tiles then you have Tile & halves not three quarter tiles.
You definitely need one t&h every other course at verges and abutments; tile gauge is 100mm therefore one t&h every 200mm.
It makes the tiler's job easier if t&h are used at hips and valleys and as a rule of thumb once again it is one t&h every other course which works out as 8 t&h per metre run of hip or valley
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