Answer:
one large box equals 15.75kg
one small box equals 13.75kg
Step-by-step explanation:
First, identify your variables:
Let "l" represent the weight of one large box.
Let"s" represent the weight of one small box.
Then, stack the two equations on top of each other:
[tex]5l+3s=120\\7l+9s=234[/tex]
Next, multiply the first equation by 3 so we can use elimination of the "s" variable to find the "l" variable first:
[tex]3(5l+3s=120)\\7l+9s=234\\\\15l+9s=360\\7l+9s=234[/tex]
Now, subtract the two equations to cancel out the s-variable and find the l-variable:
[tex]15l+9s=360\\-(7l+9s=234)\\8l=126\\\frac{8l}{8}=\frac{126}{8}\\l=15.75[/tex]
Then, substitute your l-variable in the original first equation to find the s-variable:
[tex]5l+3s=120\\5(15.75)+3s=120\\78.75+3s=120\\78.85-78.75+3s=120-78.75\\3s=41.25\\\frac{3s}{3}=\frac{41.25}{3}\\s=13.75[/tex]
With all the information that is collected, you find that one large box weighs 15.75kg and one small box weighs 13.75kg.