Having trouble with number riddles.

Question

The product of my three digits is 30.

When you add my ones digit and tens digit together

the su is my hundreds digit. My ones digit is 3.

What number am I?

Answer 1

o=3............................eq1

h*t*3=30

ht=10..................eq2

h=t+o

h=t+3..................eq3

sustituting for h in eq2 we get

(t+3)t=10

t^2+3t-10=0

t^2+5t-2t-10=0

t(t+5)-2(t+5)=0

(t-2)(t+5)=0

t=2 (or t=-5.......omit since digit cannot be -ve)

h=t+3

h=5

 

The number is hto=523