Define a new operation a $B = a + B-1, a & B = a * B-1, if x $(X & 4) = 30, x =? Everybody, hurry up

Define a new operation a $B = a + B-1, a & B = a * B-1, if x $(X & 4) = 30, x =? Everybody, hurry up

x&4=4x-1
x$(x&4)=x$(4x-1)=x+4x-1-1=5x-2=30
So x = 6.4