The answer is 90. The solution is the multiples of the other two number.

Find the missing number. ?, 12, 55; 9, 7, 4; 61, 6, 31

Find the missing number. 13, 11, 31 19, 9, 17 23, ?, 25

Find the missing number. 3 2 = 7, 5 4 = 23, 7 6 = 79, 10 9 = ?

Find the missing number. 7 6 42 35 8 3 24 16 9 2 18 9 4 5 20 ?

Find out the missing number in the picture attached: