Помогите пожалуйста 7 класс

1) $a^{2}-49=(a-7)(a+7)$
2) $64-b^{2}=(8-b)(8+b)$
3) $c^{2}-2.25=(c-1.15)(c+1.15)$
4) $2.89-d^{2}=(1.7-d)(1.7+d)$
5) $\frac{64}{81} -x^{2}=( \frac{8}{9} -x)(\frac{8}{9}+x)$
6) $\frac{100}{121} -y^{2}=( \frac{10}{11} -y)(\frac{10}{11}+y)$
7) $z^{2}- \frac{169}{196} =(z- \frac{13}{14} )(z+\frac{13}{14})$
8) $t^{2}- \frac{400}{441} =(t- \frac{20}{21} )(t+\frac{20}{21})$
9) $25x^{2}-36=(5x-6)(5x+6)$
10) $-16+49y^2=49y^2-16=(7y-4)(7y+4)$
11) $0.64- \frac{1}{9} z^2=(0.8- \frac{1}{3} z)(0.8+\frac{1}{3} z)$
12) $\frac{4}{25} t^2-36=( \frac{2}{5} t-6)(\frac{2}{5} t+6)$