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Sums of 4 (or generally $k$) unit fractions are by no means trivial.

There is a general criterion to Y. Rav (On the representation of rational numbers as a fixed sum of unit fractions. J. Reine Angew. Math. 222 (1966): 207-213.)

The equation $\frac{m}{n}= \frac{1}{x_1} + \cdots + \frac{1}{x_k}$
is certainly soluble for $m \leq k$, but for $m>k$ the same type of problems arise that one has for the Erdos-Straus equation.
One can expect that for fixed $m$ and fixed $3 \leq kN_{m,k}$ k < m$, there is some finite bound$N_{m,k}$such that$n>N_{m,k}$admits a solution. But this is an open problem. One can prove that for "almost all"$n \leq N$. The strongest version of "almost all", and a discussion of the parametrization of such equations is in C. Elsholtz, Sums of$k$unit fractions, Trans. Amer. Math. Soc. 353 (2001), 3209-3227 http://www.ams.org/journals/tran/2001-353-08/S0002-9947-01-02782-9/ 1 Sums of 4 (or generally$k$) unit fractions are by no means trivial. There is a general criterion to Y. Rav (On the representation of rational numbers as a fixed sum of unit fractions. J. Reine Angew. Math. 222 (1966): 207-213.) http://gdz.sub.uni-goettingen.de/dms/load/img/?PPN=GDZPPN00218186X&IDDOC=253620 The equation$\frac{m}{n}= \frac{1}{x_1} + \cdots + \frac{1}{x_k}$is certainly soluble for$m \leq k$, but for$m>k$the same type of problems arise that one has for the Erdos-Straus equation. One can expect that for fixed$m$and fixed$3 \leq kN_{m,k}$admits a solution. But this is an open problem. One can prove that for "almost all"$n \leq N$. The strongest version of "almost all", and a discussion of the parametrization of such equations is in C. Elsholtz, Sums of$k\$ unit fractions, Trans. Amer. Math. Soc. 353 (2001), 3209-3227