Alan

If you mean \(a=75+3^t\) then you get  \(3^t=925\)

Here you need to take the logarithm of both sides:  \(\ln{3^t}=\ln{925}\)

Now use the property of logarithms that ln mⁿ = n*ln m:   \(t\ln3=\ln{925}\)

So  \(t=\frac{\ln{925}}{\ln3}\)

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If you have \(a=75+3t^2\) and you want to find t when a = 1000, then write  

\(1000=75+3t^2\)

Rearrange this to get:  \(t^2=\frac{1000-75}{3} \rightarrow t^2=\frac{925}{3}\)  

Take the square root:   \(t=\sqrt{\frac{925}3{}}\)

Like this:

Then press Enter

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Use the Formulary here to find useful equations.  For the sphere go to: http://web2.0calc.com/formulary/math/geometry/sphere 

7593 = 3*2531  so it can be divided exactly by 3 and by 2531

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Have a look at:  http://www.s-cool.co.uk/a-level/physics/diffraction/revise-it/diffraction-from-a-diffraction-grating

x*(0.8-0.06)+0.06=0.069    

Subtract 0.06 from both sides:   x*(0.8 - 0.06) = 0.009

Simplify the term in brackets:   0.74x = 0.009

Divide both sides by 0.74:   x = 0.009/0.74   or  x = 9/740  (or x ≈ 0.012)

Solutions are:

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10 teams could come first.  For each of these, 9 could come second, making 10*9 = 90 combinations.  For each of these combinations 8 could come third.  Hence there are 10*9*8 = 720 ways.

R = D + 12                           (1)

D = B + 6                             (2)

R = 2*B                                (3)

Put (3) into (1):            2*B = D + 12            (4)

Rewrite (2) as B = D - 6 and put this into (4):             2*(D - 6) = D + 12

So:  2D - 12  = D + 12

Subtract D from both sides and add 12 to both sides to get:    D = 24

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