Question

A number consist of two digits is 15 when 18 is added to the number the digit inter change there place find the number

Answer 1

10x+y+18=10y+x
9x+18=9y::9x-9y+18=0
10x+y=15(given)::10x+y-15=0
9x-9y+18=10x+y-15(using subsitution method)
90x-90y+180=90x+9y-135
-90y+180=9y-135
315=99y
y=3.1
x=-y/10(from given)
x=-3.1/10=-0.3
no=10x+y=-3+3.1=0.1