MN = (BC+AD)/2
BC+AD = 48 - (13+15) = 20
MN = 20/2 = 10.
2) S = (BC+AD)*BM/2
98= (12+AD)*7 /2
196 = 84 + 7AD
7AD = 112
AD = 16 cm
4) S = (a+b)*h/2
a-b =8
a =8+b
S = (8+b+b)*h/2
S = (8 +2b)*h/2
108 =(8+2b)*6/2
108 = (8+2b)*3
36 = (8+2b)
36 = 8+ 2b
2b = 28
b = 14 см
а = 8+14= 22 см
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