Write an expression for 7 less than 3 times a number

7-3n

Step-by-step explanation:

It says 7 less then so that is 7 is being subtracted from 3 and it also says 3 times a number so that would be 3n.  

mother=60

daughter=20

Step-by-step explanation:

present age is 80

mother is thrice as old as her daughter when she was as old as her daughter is now

i.e 3x

then daughter is x

so 3x + x =80

4x =80

4x/4=80/4

then you cancel out with 4

therefore x is 20

mother=3x

3×20=60

then daughter=20