Problem 21

$$\begin{array}{lcl} 21.\: If\:the\:ratio\:of\:x\:to\:400\:is\:equal\:to\:the\:ratio\:of\:\\ 3\:to\:5,\:and\:if\:the\:ratio\:of\:400\:to\:y\:is\:equal\:to\:the\:\\ ratio\:of\:2\:to\:3,\:what\:is\:the\:value\:of\:x+y\:?\\ \end{array}$$