Ответ:

w(H) = 3%

w(P) = 31%

w(O) = 65%

Объяснение:

w ( эл .) = Ar ( эл .) : М ( вещества ) ⋅ 100%

М(Н3РО4) = 3*1 + 31 + 16*4 = 98

w(H) = (1*3) : 98 * 100% = 3%

w(P) = 31 : 98 * 100% = 31

w(O) = (16*4) : 98 * 100% = 65%