let her lunch = l, her gym clothes = g, her books = x
20 pounds is the amount she can carry
her lunch (1) weighs 0.75 lbs
her clothes (1) weighs 2.3 lbs
her books (x) = 3.4 lbs
Set the inequality
3.4x + 2.3 + 0.75 ≤ 20
Simplify
3.4x + 3.05 ≤ 20
3.4x + 3.05 (-3.05) ≤ 20 (-3.05)
3.4x ≤ 16.95
3.4x/3.4 ≤ 16.95/3.4
x ≤ 4.99 (rounded)
x ≤ 4.99 can be one of your inequalities.
her books can weigh up to 4.99 pounds before her backpack breaks
hope this helps