Bài tính nhanh giúp em plll

$\text{41.36 $+$ 59.90 $+$ 41.84 $+$ 59.30}$

$=$ $\text{41. (36 $+$ 84) $+$ 59. (90 $+$ 30)}$

$=$ $\text{41. 120 $+$ 59. 120}$

$=$ $\text{(41 $+$ 59).120}$

$=$ $\text{100. 120}$

$=$ $\text{12000}$

$-----------------$

$\text{4.51.7 $+$ 2.86.7 $+$ 12.2.7}$

$=$ $\text{2.7.2.51 $+$ 2.2.7.43 $+$ 2.2.7.6}$

 $=$ $\text{2.2.7. (51 $+$ 43 $+$ 6)}$

$=$ $\text{28. 100}$

$=$ $\text{2800}$

$------------------$

$\text{78.31 $+$ 78.24 $+$ 78.17 $+$ 22. 72}$

$=$ $\text{78. (31 $+$ 24 $+$ 17) $+$ 22. 72}$

$=$ $\text{78. 72 $+$ 22. 72}$ 

$=$ $\text{(78 $+$ 22). 72}$

$=$ $\text{100. 72}$

$=$ $\text{7200}$

$\text{#enid}$