Puzzles - Number puzzles

274.
Answer
:
21
Explanation
:
In each row, add the left and central numbers together, double it and add 1 to give the right hand value.

275.
Answer
:
73, 48
Explanation
:
Starting at the top, add the left and right hand numbers together and subtract 5 to give the lower left number. Add 2 to the left hand number to give the lower right hand number.

276.
Answer
:
80
Explanation
:
In each triangle, the central value equals the product of the 3 outer numbers subtracting the sum of the 3 outer numbers.