a)10²-(x-3)=4³

=>100-(x-3)=64

=>x-3=100-64

=>x-3=36

=>x=36+3

=>x=39

b)25²-(17x+82)=15²+132

=>625-(17x+82)=225+132

=>625-(17x+82)=375

=>17x+82=625-375

=>17x+82=250

=>17x=250-82

=>17x=168

=>x=168:17

=>x=168/17

c)20²-(28²-12x)=6²

=>40-(784-12x)=36

=>784-12x=40-36=4

=>12x=784-4=780

=>x=780:12=65

co len