16 weeks total
She plans to save $25 for 5 weeks. This is 25(5) = $125.
She then plans to save an extra $20, or $45, for 7 weeks. This is 45(7) = $315.
She then plans to save $25 per week for an unknown number of weeks. Letting x be this unknown number, we have 25x.
This gives us 125+315+25x.
She wants to save $540; this gives us the equation
125+315+25x = 540
Combining like terms, we have
440+25x = 540
Subtract 440 from each side:
440+25x-440 = 540-440
25x = 100
Divide both sides by 25:
25x/25 = 100/25
x = 4
She needs to save an extra 4 weeks. This makes a total time of 5+7+4 = 16 weeks.
learn more of work and time here https://brainly.com/question/1953844
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