Bob wants to build a pyramid out of legos with 3 levels where the bottom level has 7 legos per side and each level has one less lego per side than the level below it. How many legos total will he need?
First find the total number of legos on the bottom layer: 7 legos * 7 legos = <<7*7=49>>49 legos
Then find the number of legos per side on the next layer: 7 legos - 1 lego = <<7-1=6>>6 legos
Then find the total number of legos on the second level: 6 legos * 6 legos = <<6*6=36>>36 legos
Then find the number of legos per side on the top level: 6 legos - 1 lego = <<6-1=5>>5 legos
Then find the total number of legos on the top level: 5 legos * 5 legos = <<5*5=25>>25 legos
Then add the number of legos on each level to find the total number of legos: 49 legos + 36 legos + 25 legos = <<49+36+25=110>>110 legos
#### 110