5a+7b-2a-8b=7b-8b+5a-2a=-1b+3a
(4-b)(b+4)=4b+16-b^2-4b=16-b^2
(b+1)(3-2b)=3b-2b^2+3-2b=3-b-2b^2
1)23,85
2)57,766
<span>3)72,5</span>
<span>7/13+1/13=8/13
</span><span>3/10+1/7=31/70
</span>9/25+2/5=0.76
<span>1/25+3/35=22/175
</span><span>5/7-2/7=3/7
</span><span>7/9-1/4=19/36
</span><span>7/8-5/7=9/56
</span><span>7/24-7/36=7/72</span>
1) 3.805 кг
2) 6.512 кг
3) 42.389 кг