1.
2⁰+2¹+2²+....+2ˣ=2ˣ⁺¹-1
1023=2⁰+2¹+2²+....+2ˣ=2ˣ⁺¹-1
1024=2ˣ⁺¹
2¹⁰=2ˣ⁺¹
10=x+1
x=9
deci a citit cartea in 10 zile
2.
x=nr copii
5x+15=8x-18
3x=33
x=11 copii
5×11+15=55+15=70 lei costa mingea
3.
x=lungime drum
35%x=35x/100=7x/20=1 zi
x-7x/20=13x/20=rest
13x/20×20%=13x/100=a 2-a zi
7x/20+13x/100+624=x
35x+13x+62400=100x
52x=62400
x=1200 km