8дм=80см
c^2=a^2+b^2
а=60см
b=80 см
с^2=3600+6400=10000
c=100
51-19=32см
32:2=16см
Ответ:длина одной стороны 16см
1)4 2/9*2 4/7+1 2/9*2 4/7= 38/9 * 18/7 + 11/9 * 18/7 = 38/1 * 2/7 + 11/1 * 2/7 = 76/7 + 22/7 = 98/7 = 14
<span>2)2 5/6*6 2/3+3/10*6 2/3_6 2/3*1 1/3= 17/6 * 20/3 + 3/10 * 20/3 - 20/3 * 4/3 = 17/3 * 10/3 + 1/1 * 2/1 - 80/9 = 170/9 + 2 - 80/9 = 170/9 + 18/9 - 80/9 = 108/9 = 12</span>