Explicação passo-a-passo:
[tex]a) \frac{7y}{2} \times \frac{3y}{2} \times 2x = \frac{21 {y}^{2} }{4} \times 2x = \frac{42 {y}^{2}x }{4} = \frac{21 {y}^{2}x }{2} [/tex]
[tex]b) \frac{21 {y}^{2}x }{2} = \frac{21 \times {10}^{2} \times 8 }{2} = \frac{21 \times 100 \times 8}{2} = \frac{16800}{2} = 8400[/tex]
