2.(0.99-0.0 1)×(0.99+0.0 1)=0.98

3.( 1) Grandson Age ×6+6= Grandfather Age

Equation: 6X+6=66 X= 10.

(2) Dongdong's lucky money ÷3-60=360

Equation: X÷3-60=360 X= 100.

(3) (number of flowers in the first group of origami ×2+24)+ number of flowers in the first group of origami = 198.

Equation: (a×2+24)+a= 198 a=58.

4.75、76、77