Question

(p / 649.98) x 100 = 215.6

I need to find what P equals

Answer 1

As with any linear equation of this sort, multiply by the inverse of the coefficient of p.
p = 215.6*(649.98/100)
p = 1401.35688

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The above value for p will reproduce your result exactly. In some contexts, you would be asked to round it to 4 significant figures, 1401, to match the precision of the number 215.6.