[tex](100 - \frac{a}{75}) \div 35 + 1 = 876 \\ (100− \frac{a}{75} )÷35 = 875 \\ 100− \frac{a}{75} = 25 \\ \frac{a}{75} = 100 - 25 \\ \frac{a}{75} = 75 \\ a = {75}^{2} [/tex]