Answer: 30
Explanation:
Let the number be y
Add 5 to me
Y+5............equ1
Divide by 7
Y+5/7
Add 12
Y+5/7+12
Subtract 7
(Y+5)/7+(12-7)=10
12-7=5
Substitute
(Y+5)/7+5=10
Find the lowest common multiple
((Y+5)+7(5))/7=10
(Y+5)+35)/7=10
Cross multiply
Y+5+35=70
Y+40=70
Y=70-40
Y=30
The unknown number is 30