Question 162607
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{{{x=number of 2pts}}}
{{{y=number of 4pts}}}
Then, {{{2x+4y=100pts}}} ---------------------------------------> EQN 1
Also, {{{x+y=40qts}}}  -----------------------------------------> EQN 2
In EQn 2, we get {{{x=40-y}}} ----------------------------------> EQN 3
Subst. EQN 3 in EQN 1:
{{{2(40-y)+4y=100}}}
{{{80-2y+4y=100}}}
{{{2y=100-80=20}}}
{{{cross(2)y/cross(2)=cross(20)10/cross(2)}}}
{{{y=10qts}}} for 4pts
In EQN 3,
{{{x=40-10=30qts}}} for 2pts
In doubt? Go back EQN 1:
{{{2*30+4*10=100pts}}}
{{{60+40=100}}}
{{{100pts=100pts}}}
Thank you,
Jojo</pre>