Puzzles - Number puzzles

157.
Answer
:
2
Explanation
:
Reading each line of the diagram as a 3 digit number, add the top and middle lines together to give the result on the bottom line.

158.
Answer
:
1
Explanation
:
In each row, add the left and right hand numbers together and subtract 2 to give the number in the centre of the row.

159.
Answer
:
11
Explanation
:
Working through the diagram in columns, the value at the bottom of each column equals the sum of the top 2 numbers, minus the sum of the next 2 numbers.