`283xx56+252=20 xx ?`

Some equations are solved on the basis of a certain system. Find the correct answer for the unsolved equation on that basis. 5 xx 8= 28,3 xx 7 = 12,8 xx 6 = 35, 13 xx 13 = ?

In a certain codes 2 xx 3 = 56, 5 xx 6 = 1130, 8 xx 9 = 1772 , then 4 xx 1 = ?

Prove the following: (-20) xx (13 xx 4) = [(-20) xx 13] xx 4

if 56 xx 75 xx 60 xx 84 xx 210 = 2^p xx 3^q xx 5^r xx 7^s , then what is the value of [(p+q)//s]+r = ?

The product by suitable arrangement of 20xx 255 xx50 xx 7 is -

If 64 xx 52 = 17, 48 xx 56 = 23 and 74 xx 35 = 19 ,then 84 xx 37 =?

64xx52=17,48xx56=23 and 74xx35=19 , then 84xx37=?

10 xx 20 xx 30 xx 40 xx ------------- xx 1000