3x/10= 1290
Mutiply by 10 for both sides
3x/10*10= 1290*10
Cross out 10 and 10 , divide by 10 and then becomes 3x
3x=12900
divide by 3 for both sides
3x/3= 12900/3
Cross out 3 and 3 , divide by 3 and then becomes x
x= 4300
Answer: x= 4300
