4*√12 + 3*√48

simplifying the radicals, we get:

= 4*(√4)*(√3) + 3*(√4)*(√12)

the second of which can be further broken down

= 8*√3 + 6*√12

= 8*√3 + 6*(√4)*(√3)

= 8*√3 + 12*√3

= (√3)*[8 + 12]

therefore you get:

= 20*√3