Here's how I did it :
Let's consider that 112 is 76% of something that we'll name x.
This x represents the Whole which is in percentage 100% and 112 is a portion of it which is in percentage 76%
#112 -> 76%#
#x -> 100%#
Theses numbers are connected in a way that :
#x/112=(100cancel%)/(76cancel%) -> x/112= 100/76#
Same thing as : #112/x=(76cancel%)/(100cancel%) -> 112/x=76/100#
To find #x# we need the solve one of the equations above, let's say the 2nd :
#(112xxcolor(red)100)/(x xxcolor(red)100)=(76xx color(blue)x)/(100xx color(blue)x)#
Since we have the SAME denominator #(100xx x)# then the numerators must be equal.
#112xxcolor(red)100=76xx color(blue)x#
#(112xxcolor(red)100)/76=color(blue)x#
Simplify that :
#x=112/76 xx100 = (56xxcancel2)/(38xxcancel2) xx100 = (28xxcancel2)/(19xxcancel2) xx100#
19 is a prime number and is not a divisor of 2800 so:
#x=2800/19=147,368421...#
So 112 is 76% of #2800/19#