Answer:
[tex]x = 26.3 \: or \: x \: = 15.7[/tex]
Step-by-step explanation:
[tex](x - 21) ^{2} = 28 [/tex]
[tex](x - 21)(x - 21) = 28[/tex]
[tex] {x}^{2} - 42x + 441 = 28[/tex]
[tex] {x }^{2} - 42x + 441 - 28 = 0[/tex]
[tex] {x}^{2} - 42x - 413 = 0[/tex]
