Question

please answer q no. 6,7,8 ..

Answer 1

6) let the unit place digit of number be x &tens place be y
so number become 10y+x
by reversing the digits the number become 10x+y
7(10y+x) =4(10x+y)
70y+7x=40x+4y
66y=33x
2y=x
2y-x=0 .......... (2)
y+x=3 ........ (1)
add 1 and 2
3y=3
y=1
x=2
so number is 12

Answer 2

6) let the unit place digit of number be x &tens place be y
so number become 10y+x
by reversing the digits the number become 10x+y
7(10y+x) =4(10x+y) 
70y+7x=40x+4y
66y=33x
2y=x
2y-x=0 .......... (2) 
y+x=3 ........ (1) 
add 1 and 2
3y=3
y=1
x=2
so number is 12