Its very simple middle element is the sum of the corner elements in the triangle i.e. 50+30+10 =90 On the similar line missing element is 30 (90 - 40 - 20).

Sum if triangle is 90 so answer is 30.

By deducing the logic used in the table below, can you find the missing number?

Find the missing number in the following grid?

Look at the numbers given in the picture and find the missing number.

Find the value of each and then find the value of the missing number.

Find the logic and then find the value of the missing number ‘X’.