so first distribute (2/3a-0.8)(a-0.8)=0.64 focus on the left side
(2/3a-0.8)(a-0.8)= (a)(2/3a-0.8)+(-0.8)(2/3a-0.8)= (2/3a^2)+(-0.8a)+(-1.6/3a)+(0.64)= 2/3a^2-4/3a+0.64 now we do 2/3a^2-4/3a+0.64=0.64 minus 0.64 both sides 2/3a^2-4/3a=0 factor (a)(2/3a-4/3)=0 set each to zero a=0
2/3a-4/3=0 add 4/3 both sides 2/3a=4/3 times 3 bohth sides 2a=4 divide 2 a=2