This monograph is a study in analytical number theory, related to the field of the theory of short trigonometric sums, and its applications to classical additive problems with more stringent conditions, namely, when the terms are almost equal. Short trigonometric sums that arise when solving additive problems with almost equal terms were first studied by I. M. Vinogradov. The relevance and appropriateness of this monograph are determined by the fact that it- studied the behavior of G. Weyl's short trigonometric sums of the formT( ,x,y)= _(x-yin large arcs;- the results obtained made it possible to find an asymptotic formula for the number of representations of a sufficiently large natural number as a sum of three almost equal terms, two of which are prime numbers, and the third is the fourth power of a natural number.