Răspuns:
267/361
200
Explicație pas cu pas:
problema 1
a=((3/2)²-(1/2)²)*(9/19)=(9/4-1/4) *(9/19)=(8/4) *(9/19)=2*9/19=18/19
2a²-1=2(18/19)²-1=2*324/361-1=(628-361)/361=267/361
cam uratica, ciudatica
problema 2
S-30S/100-20S/100-25S/100=50
S=75S/100=50
S-3S/4=50
S/4=50
S=200 lei