So first it is a 2 digit number so think of numbers from 10-99 then if u add them its 15 and if multiplied it is 56
let x=first digit
let y=second digit
x+y=15
then the other one is
xy=15
so first lets start with xy=15
xy=15
divide both sides by y
x=15/y
x+y=15
15/y+y=15
15/y+y^2/y=15
(15+y^2)/y=15
Multiply both sides by y
15+y^2=15y
y^2-15y+15=0
(y-8)(y-7)=0
y=7 y=8
Substitute it from first equation
x+y=15
x+7=15
x=8
x+y=15
x+8=15
x=7
There for it must be vice versa so it should be 78 where 7 is the x and 8 is the y and 87 where x is 8 and 7 is y
