I think you are confusing summarise() with mutate() function, to help us help you, could you please prepare a reproducible example (reprex) illustrating your issue? Please have a look at this guide, to see how to create one:
EDIT: I think this example with built-in data is very close to what you are trying to do
library(dplyr)
library(magrittr)
iris %>%
mutate(aDOT = Sepal.Length / Sepal.Width,
yac_per_rec = Petal.Length / Petal.Width) %$%
lm(aDOT ~ yac_per_rec) %>%
summary()
#>
#> Call:
#> lm(formula = aDOT ~ yac_per_rec)
#>
#> Residuals:
#> Min 1Q Median 3Q Max
#> -0.71340 -0.17850 -0.00652 0.15870 0.87885
#>
#> Coefficients:
#> Estimate Std. Error t value Pr(>|t|)
#> (Intercept) 2.37802 0.05201 45.722 <2e-16 ***
#> yac_per_rec -0.09844 0.01046 -9.414 <2e-16 ***
#> ---
#> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#>
#> Residual standard error: 0.3178 on 148 degrees of freedom
#> Multiple R-squared: 0.3745, Adjusted R-squared: 0.3703
#> F-statistic: 88.62 on 1 and 148 DF, p-value: < 2.2e-16