3x=90 x= 30 ...(1)
30 -2x=20, 2x=-10, x=5 ....(2)
5+ x²=25, x²=20, x=√20=4.472 ....(3)
√20 - (30 x 5) = 4.472-150 = - 145.528
Since the definition is not given in the last line, then the following must be assumed following mathematical principles. (Multiplication before addition/subtraction)