If the 8-digit number 179x091y is divisible by 88, the value of (5x — 8y) is:

Given that,

179x091y is divisible by 88.

We know that $$88=11\times 8$$

The given number will be divisible by 88, if it is individually divisible by 11 and 8.

Divisibility by 8 - Any number is divisible by 8, if the last 3 digit of that number is divisible by 8.

So, last 3 digit is 91y,

91y will be divisible by 8 if, y=2,

Divisibility by 11- Any number is divisible by 11, if the difference between the sum of odd place digit and sum of even place digit is
divisible by 11.

179x091y will be divisible by 11 if $$y+9+x+7-1-0-9-1=y+x+5=x+7$$

From the above, if x=4, then it will be divisible by 11.

Hence the value of x and y will be 4 and 2.

Hence,$$ (5x — 8y)=5\times4-8\times 2=20-16=4$$