Question 263592
This is a money equation. We need two equations.
(i) {{{10d + 25q = 1025}}}
(ii) {{{q = 2d - 7}}}
step 1 - substitute (ii) into (i) to get
(iii) {{{10d + 25(2d-7) = 1025}}}
step 2 - distribute to get
(iv) {{{10d + 50d - 175 = 1025}}}
step 3 - combine like terms to get
(v) {{{60d -175 = 1025}}}
add 175 to get
 (vi) {{{60d = 1200}}}
d = 20
and from (ii) 
q = 33