Tìm x: \( x + 5 + 2 = 650 \), \( B_3^{\frac{1}{2}}: \left( 4 - \frac{1}{3}(7 + 2x) \right) = \frac{21}{22} \)

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5) Tìm x:
a) \( x + 5 + 2 = 650 \)

b) \( B_3^{\frac{1}{2}}: \left( 4 - \frac{1}{3}(7 + 2x) \right) = \frac{21}{22} \)

c) Tìm x, y, z biết x + y + z = 3; y + z = 4; 5u + xy = 2 = 5.