a) $2020^{5}$(x-60)=$2020^{6}$
x-60=$2020^{6}$:$2020^{5}$=2020
x=2020+60=2080
Vậy x=2080
b) 720:[41-(2x-5)]=$2^{3}$.5
720:[41-(2x-5)]=40
41-(2x-5)=720:40=18
2x-5=41-18=23
2x=23+5=28
x=28:2=14
Vậy x=14
c) 5x+3(10-x)+x=45
5x+30-3x+x=45
5x-3x+x=45-30=15
3x=15
x=15:3=5
Vậy x=5