To write inequalities for the given problems, we need to analyze the conditions and constraints mentioned in the problem. Here are the inequalities for each problem:
2. Quiz Grades:
Let's assume the lowest grade on the next quiz as "x". We know that the average of the quiz grades should be at least 18. So, the inequality is:
(19 + 17 + 20 + 15 + x) / 5 ≥ 18
3. Volunteer Hours:
Let's assume Luis worked for "x" hours. Since Stacey worked 4 more hours than Luis, her hours would be "x + 4". Together, they worked for more than 28 hours, so the inequality is:
x + (x + 4) > 28
4. Saving Money:
Let's assume the younger son saved "x" dollars. According to the condition, the older son agreed to save twice as much as the younger one, so he would save "2x" dollars. Together, they have to save more than $45, so the inequality is:
x + 2x > 45
Remember, these inequalities represent the conditions mentioned in the problems, but they are not solved. Solving them will give you the specific values that satisfy the inequalities.