Question 107603
Let's use o for the number of calories in an orange, and p for the number of calories in a peach.


We are given that {{{o=p+30}}} and {{{13p = 7o}}}


Eq 1) {{{o-p-30=0}}}

Eq 2) {{{7o - 13p=0}}}


Multiply Eq 1) by -7


Eq 3) {{{-7o+7p+210=0}}}


Now add Eq 2) and Eq 3) term by term to eliminate the o term.


{{{-6p+210=0}}}
{{{6p=210}}}
{{{p=35}}}
{{{o=35+30=65}}}


Check:


{{{13*35=455}}}
{{{7*65=455}}}