Question 268974
we need two equations
(i) {{{D + Q = 60}}}
(ii) {{{10D + 25Q = 945}}}
step 1 - multiply (i) by -10 to get
(iii) {{{-10D - 10Q = -600}}}
step 2 - add (ii) and (iii) to get
(iv) {{{15Q = 345}}}
step 3 - divide by 15 to get
(v) {{{Q = 23}}}
Since Q =23, we know that
(vi) {{{ D = 37}}}