Question 262168
let t=ten's digit and u equal units digit.
t=3u
8(t+u)=10t+u-1
8t+8u=10t+u-1
7u=2t-1
7u=2*(3u)-1
7u=6u-1
u=-1
t=-3
the number is -31
check
8(-3-1)=-31=1
8*-4=-32
-32=-32
So why are you hiding the answer you were given?

It turns out that the original problem says three greater and not three times greater
so picking up the problem

7u=2t-1
t=3+u
7u=2(3+u)-1
7u=6 +2u-1
5u=5
u=1
t=3+u
t=3+1
t=4
check
8*(4+1)=41-1
40=40
ok