a) 10/3 * ? = 8 | : (10/3)
? = 8 : (10/3) = 8/1 * 3/10 = (8*3)/10 = (4*3)/5 = 12/5
usw.
b) ? * 3/5 = 7/10 | :(3/5)
? = (7/10) : (3/5) = (7/10) * (5/3) = (7*5)/(10*3) = 7/(2*3) = 7/6
c) 3/8 + ? = 2/3 | - 3/8
? = (2/3) - (3/8) = (16/24) - (9/24) = (16-9)/24 = 7/24
Bitte selber nachrechnen!